v3.26.1
Cover - shares
 3 Months Ended
Mar. 31, 2026
May 07, 2026
Document Information [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2026  
Document Transition Report false  
Entity File Number 001-42175  
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  
Title of 12(b) Security Voting Common Stock, $0.0001 Par Value  
Trading Symbol FSUN  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Entity Shell Company false  
Entity Central Index Key 0001709442  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q1  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Voting Common Stock    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   44,123,875
Non-voting Common Stock    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   2,612,830