Long term debt, net - Narrative 1 (Details) $ / shares in Units, $ in Thousands		9 Months Ended
	Mar. 27, 2025 d	Sep. 30, 2025 USD ($) $ / shares shares	Sep. 30, 2024 USD ($)	Mar. 12, 2025 USD ($) $ / shares shares
Long term debt
Warrants issued \| shares		37,182,036
Debt Instrument, Redemption Price, Percentage	100.00%
Gain (Loss) on Extinguishment of Debt \| $		$ (13,734)
Note Purchase Agreement [Member] \| Private Placement [Member] \| Purchasers [Member]
Long term debt
Debt Instrument, Aggregate principal amount \| $				$ 190,000
Note Purchase Agreement [Member] \| Common stock purchase warrants [Member] \| Private Placement [Member]
Long term debt
Common Stock, Par or Stated Value Per Share				$ 0.0001
Common stock issuable for warrant exercise \| shares				7,800,000
Warrants issued \| shares		7,800,000
Note Purchase Agreement [Member] \| Common stock purchase warrants [Member] \| Private Placement [Member] \| Minimum [Member]
Long term debt
Exercise price of warrants issued		$ 12.56		$ 12.56
Note Purchase Agreement [Member] \| Common stock purchase warrants [Member] \| Private Placement [Member] \| Maximum [Member]
Long term debt
Exercise price of warrants issued		$ 20		$ 20
Note Purchase Agreement [Member] \| Senior Secured Notes due 2026 [Member]
Long term debt
Debt Instrument, Aggregate principal amount \| $		$ 70,000
Debt Instrument, Interest Rate, Stated Percentage		10.00%
Debt Instrument, Maturity Date		Dec. 01, 2026
Debt Instrument, Frequency of Periodic Payment		semi-annually
Debt Instrument, Redemption Price, Percentage	101.00%
Gain (Loss) on Extinguishment of Debt \| $		$ 14,400
Note Purchase Agreement [Member] \| Senior Secured Notes due 2026 [Member] \| Maximum [Member]
Long term debt
Percentage of accrued and unpaid interest on debt		50.00%
Note Purchase Agreement [Member] \| Senior Secured Notes due 2026 [Member] \| Debt Warrants 2026 [Member]
Long term debt
Warrants issued \| shares		25,925,927
Exercise price of warrants issued		$ 2.16
Warrant redemption price per share of underlying common stock		$ 0.01
Note Purchase Agreement [Member] \| Senior Secured Notes due 2026 [Member] \| Debt Warrants 2026 [Member] \| Minimum [Member]
Long term debt
Debt Instrument, Redemption Price, Percentage		130.00%
Note Purchase Agreement [Member] \| Senior Secured Convertible Notes due 2028 [Member]
Long term debt
Debt Instrument, Interest Rate, Stated Percentage	5.00%
Debt Instrument, Maturity Date	Jun. 30, 2028
Debt Instrument, Frequency of Periodic Payment	semi-annually
Note Purchase Agreement [Member] \| Senior Secured Convertible Notes due 2028 [Member] \| Warrant [Member] \| Maximum [Member]
Long term debt
Exercise period of debt issued, from date of initial closing		35 days
Note Purchase Agreement [Member] \| Senior Secured Convertible Notes due 2028 [Member] \| Private Placement [Member]
Long term debt
Debt Instrument, Interest Rate, Stated Percentage				5.00%
Indenture and Security Agreement [Member] \| Senior Secured Convertible Notes due 2028 [Member] \| Private Placement [Member] \| Guarantors and GLAS Trust Company, LLC [Member]
Long term debt
Debt Instrument, Convertible, Threshold Trading Days \| d	20
Debt Instrument, Convertible, Threshold Consecutive Trading Days \| d	30
Indenture and Security Agreement [Member] \| Senior Secured Convertible Notes due 2028 [Member] \| Private Placement [Member] \| Guarantors and GLAS Trust Company, LLC [Member] \| Minimum [Member]
Long term debt
Debt instrument, Redemption price, Percentage of conversion price	160.00%

NEXTNAV INC. 10-Q