Cover - shares	9 Months Ended
	Sep. 30, 2022	Nov. 09, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2022
Document Transition Report	false
Entity File Number	333-258176
Entity Registrant Name	FIRSTSUN CAPITAL BANCORP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-4552413
Entity Address, Address Line One	1400 16th Street
Entity Address, Address Line Two	Suite 250
Entity Address, City or Town	Denver
Entity Address, State or Province	CO
Entity Address, Postal Zip Code	80202
City Area Code	303
Local Phone Number	831-6704
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		24,906,032
Entity Central Index Key	0001709442
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q3
Amendment Flag	false
Current Fiscal Year End Date	--12-31