Subordinated Debentures - Schedule of Subordinated Debentures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Terms of Subordinated Debentures
Balance	$ 132,620	$ 139,959
Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	132,620
First Company Statutory Trust 2001 | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 3,521
Rate	3.432%
Rate Structure	3.30%
First Company Statutory Trust 2003 | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 2,587
Rate	3.47%
Rate Structure	3.25%
Glacier Capital Trust II | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 46,393
Rate	2.874%
Rate Structure	2.75%
Citizens (ID) Statutory Trust I | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 5,155
Rate	2.866%
Rate Structure	2.65%
Glacier Capital Trust III | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 36,083
Rate	1.414%
Rate Structure	1.29%
Glacier Capital Trust IV | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 30,928
Rate	1.773%
Rate Structure	1.57%
Bank of the San Juans Bancorporation Trust I | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 2,041
Rate	1.991%
Rate Structure	1.82%
FNB (UT) Statutory Trust I | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 4,124
Rate	3.32%
Rate Structure	3.10%
FNB (UT) Statutory Trust II | Subordinated debentures owed to trust subsidiaries
Terms of Subordinated Debentures
Balance	$ 1,788
Rate	1.923%
Rate Structure	1.72%