Document And Entity Information	4 Months Ended
	Sep. 30, 2021
Document Information Line Items
Entity Registrant Name	NEXTNAV INC.
Document Type	S-1
Amendment Flag	false
Entity Central Index Key	0001865631
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Incorporation, State or Country Code	DE