Subordinated Debentures - Schedule of Subordinated Debentures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Terms of Subordinated Debentures
Balance	$ 132,943	$ 132,782
Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	132,943
First Company Statutory Trust 2001 | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 3,647
Rate 1	8.945%
Rate Structure	3.30%
First Company Statutory Trust 2003 | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 2,676
Rate 1	8.872%
Rate Structure	3.25%
Glacier Capital Trust II | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 46,393
Rate 1	8.405%
Rate Structure	2.75%
Citizens (ID) Statutory Trust I | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 5,155
Rate 1	8.289%
Rate Structure	2.65%
Glacier Capital Trust III | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 36,083
Rate 1	6.945%
Rate Structure	1.29%
Glacier Capital Trust IV | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 30,928
Rate 1	7.216%
Rate Structure	1.57%
Bank of the San Juans Bancorporation Trust I | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 2,112
Rate 1	7.459%
Rate Structure	1.82%
FNB (UT) Statutory Trust I | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 4,124
Rate 1	8.722%
Rate Structure	3.10%
FNB (UT) Statutory Trust II | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 1,825
Rate 1	7.366%
Rate Structure	1.72%