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Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.

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Stockholders' Equity - Narrative (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2026 USD ($) company $ / shares shares	Mar. 31, 2025 USD ($)	Dec. 31, 2025 $ / shares shares	Dec. 31, 2021 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock, shares authorized (in shares)	10,000,000		10,000,000
Preferred stock, par value (in dollars per share) \| $ / shares	$ 0.0001		$ 0.0001
Preferred stock, shares outstanding (in shares)	0		0
Preferred stock, shares issued (in shares)	0		0
Dividends, term without prior regulatory approval, preceding period of net income	2 years
Total unrecognized compensation cost related to non-vested stock options granted \| $	$ 3,960
Option awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award contractual term	10 years
Option awards \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, number of comparable companies \| company	25
Option awards \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, number of comparable companies \| company	30
Option awards \| First Anniversaries
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	25.00%
Option awards \| Second Anniversaries
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	25.00%
Option awards \| Third Anniversaries
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	25.00%
Option awards \| Fourth Anniversaries
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	25.00%
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized share-based compensation cost related to unvested restricted stock units \| $	$ 3,845
FirstSun Capital Bancorp 2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate shares of common stock (in shares)	1,977,292
Total unrecognized compensation cost related to non-vested stock options granted \| $	$ 0
Intrinsic value of the stock options \| $	10,653	$ 14,089
FirstSun Capital Bancorp 2021 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate shares of common stock (in shares)				2,476,571
Pioneer's Option Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of the stock options \| $	120	1,167
FirstSun Capital Bancorp 2017 And 2021 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based payment arrangement, compensation cost \| $	$ 1,255	$ 636
Voting Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized (in shares)	80,000,000		50,000,000
Common stock, par value (in dollars per share) \| $ / shares	$ 0.0001		$ 0.0001
Common stock, shares issued (in shares)	27,935,888		27,887,337
Common stock, shares outstanding (in shares)	27,935,888		27,887,337
Non-voting Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized (in shares)	20,000,000		0
Common stock, shares issued (in shares)	0		0
Common stock, shares outstanding (in shares)	0		0