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AT&T Agreement (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended		12 Months Ended
	Oct. 28, 2021	Jan. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Jun. 30, 2021
AT&T Agreement (Details) [Line Items]
AT&T Agreements, Description			The AT&T Agreements provide for: (i) AT&T’s marketing and resale of services to FirstNet® subscribers and certain pricing requirements for the Company’s software development kits (“SDK”) based on the quantity of usage, revenue sharing, compliance with data rights and privacy, and support requirements; and (ii) AT&T hosting of weather measurement equipment for altitude determination at AT&T sites, at no recurring cost to NextNav for a 7-year lease term.
Cash consideration				$ 2.000
Equipment term				7 years
Termination term				3 years
Sale-leaseback financing method				$ 4.7
Minimum lease payments		$ 5.5	$ 5.0
Exercise price			$ 0.01
AT&T Warrants vested percentage	50.00%	30.00%	10.00%	60.00%
Interest rate percentage					6.00%
Warrant liability			$ 4.4
Sale price, per share	$ 12
Business Combination [Member]
AT&T Agreement (Details) [Line Items]
Minimum lease payments			$ 3.5
AT&T Holdings [Member]
AT&T Agreement (Details) [Line Items]
AT&T Warrants vested percentage			30.00%
Warrant [Member]
AT&T Agreement (Details) [Line Items]
Exercise price			$ 11.5
AT&T Warrants vested percentage			10.00%
Class D Redeemable Preferred Units [Member]
AT&T Agreement (Details) [Line Items]
Warrants purchase shares			21,221,299
Exercise price			$ 2.89
Granted additional warrants to purchase stock				1,910,158
Class A Common Stock [Member]
AT&T Agreement (Details) [Line Items]
Exercise price			$ 0.01
Granted additional warrants to purchase stock			4,320,133
Warrant issued			6,947,447
Class D Redeemable Preferred Stock [Member]
AT&T Agreement (Details) [Line Items]
Interest rate percentage			66.60%
Fair value			$ 12.6	$ 11.0