Fair value estimates- Additional Quantitative Information about Assets Measured at Fair Value on Nonrecurring Basis (Detail) - Fair Value Measurements Nonrecurring [Member] - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Estimate	$ 6,054	$ 422
Other Real Estate Owned [Member] \| Level 3 Fair Value Measurements, Appraisal Adjustments [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Estimate	$ 219	$ 422
Valuation Technique	Appraisal of collateral	Appraisal of collateral
Unobservable Input	Appraisal adjustments	Appraisal adjustments
Other Real Estate Owned [Member] \| Level 3 Fair Value Measurements, Liquidation Expenses [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Unobservable Input	Liquidation expenses	Liquidation expenses
Impaired Loan [Member] \| Level 3 Fair Value Measurements, Appraisal Adjustments [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Estimate	$ 5,835
Valuation Technique	Appraisal of collateral
Unobservable Input	Appraisal adjustments
Impaired Loan [Member] \| Level 3 Fair Value Measurements, Liquidation Expenses [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Unobservable Input	Liquidation expenses
Minimum [Member] \| Other Real Estate Owned [Member] \| Level 3 Fair Value Measurements, Appraisal Adjustments [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Range (Weighted Average)	0.00%	20.00%
Minimum [Member] \| Other Real Estate Owned [Member] \| Level 3 Fair Value Measurements, Liquidation Expenses [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Range (Weighted Average)	10.00%	10.00%
Minimum [Member] \| Impaired Loan [Member] \| Level 3 Fair Value Measurements, Appraisal Adjustments [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Range (Weighted Average)	0.00%
Minimum [Member] \| Impaired Loan [Member] \| Level 3 Fair Value Measurements, Liquidation Expenses [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Range (Weighted Average)	7.00%
Maximum [Member] \| Other Real Estate Owned [Member] \| Level 3 Fair Value Measurements, Appraisal Adjustments [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Range (Weighted Average)	3.00%	14.00%
Maximum [Member] \| Other Real Estate Owned [Member] \| Level 3 Fair Value Measurements, Liquidation Expenses [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Range (Weighted Average)	10.00%	10.00%
Maximum [Member] \| Impaired Loan [Member] \| Level 3 Fair Value Measurements, Appraisal Adjustments [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Range (Weighted Average)	0.00%
Maximum [Member] \| Impaired Loan [Member] \| Level 3 Fair Value Measurements, Liquidation Expenses [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Range (Weighted Average)	7.00%
Weighted Average [Member] \| Other Real Estate Owned [Member] \| Level 3 Fair Value Measurements, Appraisal Adjustments [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Range (Weighted Average)	3.00%	8.40%
Weighted Average [Member] \| Other Real Estate Owned [Member] \| Level 3 Fair Value Measurements, Liquidation Expenses [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Range (Weighted Average)	10.00%	10.00%
Weighted Average [Member] \| Impaired Loan [Member] \| Level 3 Fair Value Measurements, Appraisal Adjustments [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Range (Weighted Average)	0.00%
Weighted Average [Member] \| Impaired Loan [Member] \| Level 3 Fair Value Measurements, Liquidation Expenses [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Range (Weighted Average)	7.00%

Riverview Financial Corp 10-Q