Merger with Pioneer Bancshares, Inc. - Estimated Fair Values of the Assets Acquired and Liabilities Assumed in this Transaction (Details) - USD ($) $ in Thousands	Apr. 01, 2022	Sep. 30, 2022	Dec. 31, 2021
Business Acquisition [Line Items]
Goodwill		$ 93,483	$ 33,050
FirstSun Capital Bancorp and Pioneer Bancshares, Inc. Merger
Business Acquisition [Line Items]
Cash and cash equivalents	$ 449,278
Investment securities	157,859
Loans held-for-sale	2,923
Loans	811,300
Premises and equipment	39,935
Bank-owned life insurance	21,382
Restricted equity securities	9,320
Core deposits and other intangible assets	11,771
Accrued interest receivable	3,947
Deferred tax assets	19,752
Prepaid expenses and other assets	7,317
Total assets acquired	1,534,784
Deposits	1,192,081
Federal Home Loan Bank advances	159,924
Accrued interest payable	407
Accrued expenses and other liabilities	1,975
Total liabilities assumed	1,354,387
Fair value of net assets acquired	180,397
Purchase price	240,830
Goodwill	$ 60,433