Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2021	Mar. 18, 2022	Jun. 30, 2021
Document Information Line Items
Entity Registrant Name	NextNav Inc.
Trading Symbol	NN
Document Type	10-K
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		95,553,763
Entity Public Float			$ 0
Amendment Flag	false
Entity Central Index Key	0001865631
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	No
Document Period End Date	Dec. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Shell Company	false
Entity Ex Transition Period	false
ICFR Auditor Attestation Flag	false
Document Annual Report	true
Document Transition Report	false
Entity File Number	001-40985
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	87-0854654
Entity Address, Address Line One	1775 Tysons Blvd
Entity Address, Address Line Two	5th Floor
Entity Address, City or Town	McLean
Entity Address, State or Province	VA
Entity Address, Postal Zip Code	22102
City Area Code	(800)
Local Phone Number	775-0982
Title of 12(b) Security	Common Stock, $0.0001 par value
Security Exchange Name	NASDAQ
Entity Interactive Data Current	Yes
Auditor Firm ID	42
Auditor Name	Ernst & Young LLP
Auditor Location	Tysons, Virginia