Basis of Presentation (Policies)	6 Months Ended
Basis of Presentation (Policies)	Jun. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Reclassifications	Reclassifications Certain prior-period amounts have been reclassified to conform to the current period presentation. Such reclassifications had no impact on the Company’s reported total revenues, expenses, net loss, current assets, total assets, current liabilities, total liabilities or stockholders’ equity.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted CashThe Company considers all highly-liquid investments to be cash equivalents if they have maturities of three months or less when purchased.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The carrying value of long-lived assets and certain identifiable intangibles are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. When it is determined that the estimated future net cash flows of an asset will not be sufficient to recover its carrying amount, an impairment loss must be recorded to reduce the carrying amount to its estimated fair value. Judgments and assumptions are inherent in management’s estimate of undiscounted future cash flows and an asset’s fair value. These judgments and assumptions include such matters as the estimation of oil and gas reserve quantities, risks associated with the different categories of oil and gas reserves, the timing of development and production, expected future commodity prices, capital expenditures, production costs, and appropriate discount rates. The Company evaluates impairment of proved and unproved oil and gas properties on a region basis. On this basis, certain regions may be impaired because they are not expected to recover their entire carrying value from future net cash flows. As a result of this evaluation, the Predecessor recorded impairment of oil and gas properties of $199.9 million for the three months ended March 31, 2020, of which $199.0 million was proved and $0.9 million was unproved. The impairment was the result of removing development of proved undeveloped reserves (“PUDs”) and probable reserves from future net cash flows as the Predecessor could not assure that they would be developed going forward in light of continued depressed commodity prices and uncertainty regarding the Predecessor’s liquidity situation at the time. Upon emergence from bankruptcy, the Company adopted fresh start accounting which resulted in its long-lived assets being recorded at their estimated fair value at the Effective Date. There were no material changes to the key cash flow assumptions and no triggering events since December 31, 2020; therefore, no impairment was identified in the three or six months ended June 30, 2021.
Net Income (Loss) per Common Share	Net Loss per Common Share Prior to the Effective Date, the Predecessor company used the two-class method to compute earnings per common share as its Class A Participating Preferred Stock (the “Preferred Stock”) was considered a participating security. Under the two-class method, losses are allocated only to those securities that have a contractual obligation to share in the losses of the Company. The Preferred Stock was not obligated to absorb Company losses and accordingly was not allocated losses. Net income attributable to common stockholders is allocated between common stock and participating securities based on the weighted average number of common shares and participating securities outstanding for the period. Upon the Effective Date, the Preferred Stock was extinguished and the two-class method is no longer necessary to compute earnings per share for the Successor. Basic earnings per share is computed by dividing the allocated net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding for the period. Diluted earnings per share is computed similarly except that the denominator is increased to include dilutive potential common shares. Potential common shares for the Predecessor consisted of warrants, equity compensation awards and preferred stock, while potential common shares for the Successor consist of warrants. In certain circumstances adjustment to the numerator is also required for changes in income or loss resulting from the potential common shares. Basic weighted average common shares exclude shares of non-vested restricted stock. As these restricted shares vest, they will be included in the shares outstanding used to calculate basic earnings per share.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Income Taxes. In December 2019, the Financial Accounting Standards Board (“FASB”) issued ASU 2019-12, Income Taxes (Topic 740) – Simplifying the Accounting for Income Taxes (“ASU 2019-12”). The objective of ASU 2019-12 is to simplify the accounting for income taxes by removing certain exceptions to the general principles in Topic 740 and to provide more consistent application to improve the comparability of financial statements. The amendments in this ASU were effective starting January 1, 2021 for the Company. Financial Instruments — Credit Losses. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (“ASU 2016-13”). ASU 2016-13 changes the impairment model for most financial assets and certain other instruments, including trade and other receivables, and requires the use of a new forward-looking expected loss model that will result in the earlier recognition of allowances for losses. The amendments in this ASU are effective for fiscal years beginning after December 15, 2022 for Smaller Reporting Companies, which the Company currently is classified as, and interim periods within those fiscal years, and early adoption is permitted. Entities must adopt the amendment using a modified retrospective approach to the first reporting period in which the guidance is effective. The adoption of ASU 2016-13 is currently not expected to have a material effect on the Company’s Unaudited Condensed Consolidated Financial Statements. Reference Rate Reform. In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848) (“ASU 2020-04”). ASU 2020-04 provides optional expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions to ease financial reporting burdens related to the expected market transition from the London Interbank Offered Rate (“LIBOR”) or another reference rate to alternative reference rates. The amendments in this ASU were effective upon issuance and generally can be applied to applicable contract modifications through December 31, 2022. Currently, the Company’s Successor Credit Agreements (as defined below) are the Company’s only contracts that makes reference to a LIBOR rate and the agreements outline the specific procedures that will be undertaken once an appropriate alternative benchmark is identified. The Company does not expect this guidance to have a significant impact on its Unaudited Condensed Consolidated Financial Statements and related footnote disclosures.
Fair Value Measurements	Fair Value Measurements Fair value measurements are based upon inputs that market participants use in pricing an asset or liability, which are classified into two categories: observable inputs and unobservable inputs. Observable inputs represent market data obtained from independent sources, whereas unobservable inputs reflect a company’s own market assumptions, which are used if observable inputs are not reasonably available without undue cost and effort. Accounting Standards Codification (“ASC”) 820 prioritizes the inputs used in measuring fair value into the following fair value hierarchy: •Level 1 – Quoted prices for identical assets or liabilities in active markets. •Level 2 – Quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability, and inputs derived principally from or corroborated by observable market data by correlation or other means. •Level 3 – Unobservable inputs for the asset or liability. The fair value input hierarchy level to which an asset or liability measurement falls in its entirety is determined based on the lowest level input that is significant to the measurement in its entirety.

Lonestar Resources US Inc. 10-Q