Subordinated Debentures - Schedule of Subordinated Debentures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Terms of Subordinated Debentures
Balance	$ 133,105	$ 132,943
Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	133,105
First Company Statutory Trust 2001 | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 3,710
Rate	8.147%
Rate Structure	3.30%
First Company Statutory Trust 2003 | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 2,722
Rate	8.171%
Rate Structure	3.25%
Glacier Capital Trust II | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 46,393
Rate	7.668%
Rate Structure	2.75%
Citizens (ID) Statutory Trust I | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 5,155
Rate	7.261%
Rate Structure	2.65%
Glacier Capital Trust III | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 36,083
Rate	6.208%
Rate Structure	1.29%
Glacier Capital Trust IV | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 30,928
Rate	6.191%
Rate Structure	1.57%
Bank of the San Juans Bancorporation Trust I | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 2,147
Rate	6.581%
Rate Structure	1.82%
FNB (UT) Statutory Trust I | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 4,124
Rate	8.021%
Rate Structure	3.10%
FNB (UT) Statutory Trust II | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 1,843
Rate	6.341%
Rate Structure	1.72%