Regulatory Capital (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Total capital (to risk-weighted assets)
Actual, Amount	$ 923,574	$ 883,954
Actual, Ratio	20.09%	20.27%
Minimum capital requirement, Amount	367,701	348,950
Minimum capital requirement, Ratio	8.00%	8.00%
Well capitalized requirement, Amount	459,627	436,187
Well capitalized requirement, Ratio	10.00%	10.00%
Tier 1 capital (to risk-weighted assets)
Actual, Amount	865,213	828,404
Actual, Ratio	18.82%	18.99%
Minimum capital requirement, Amount	183,851	174,475
Minimum capital requirement, Ratio	4.00%	4.00%
Well capitalized requirement, Amount	275,776	261,712
Well capitalized requirement, Ratio	6.00%	6.00%
Tier 1 capital (to average assets)
Actual, Amount	865,213	828,404
Actual, Ratio	11.31%	11.81%
Minimum capital requirement, Amount	306,005	280,602
Minimum capital requirement, Ratio	4.00%	4.00%
Well capitalized requirement, Amount	5.00%
Glacier Bank [Member]
Total capital (to risk-weighted assets)
Actual, Amount	851,819	187,082
Actual, Ratio	18.79%	19.95%
Minimum capital requirement, Amount	362,711	75,033
Minimum capital requirement, Ratio	8.00%	8.00%
Well capitalized requirement, Amount	453,388	93,792
Well capitalized requirement, Ratio	10.00%	10.00%
Tier 1 capital (to risk-weighted assets)
Actual, Amount	794,228	175,066
Actual, Ratio	17.52%	18.67%
Minimum capital requirement, Amount	181,355	37,517
Minimum capital requirement, Ratio	4.00%	4.00%
Well capitalized requirement, Amount	272,033	56,275
Well capitalized requirement, Ratio	6.00%	6.00%
Tier 1 capital (to average assets)
Actual, Amount	794,228	175,066
Actual, Ratio	10.55%	13.00%
Minimum capital requirement, Amount	301,013	53,846
Minimum capital requirement, Ratio	4.00%	4.00%
Well capitalized requirement, Amount	376,267	67,308
Well capitalized requirement, Amount	5.00%	5.00%
Mountain West Bank [Member]
Total capital (to risk-weighted assets)
Actual, Amount		149,280
Actual, Ratio		20.42%
Minimum capital requirement, Amount		58,474
Minimum capital requirement, Ratio		8.00%
Well capitalized requirement, Amount		73,092
Well capitalized requirement, Ratio		10.00%
Tier 1 capital (to risk-weighted assets)
Actual, Amount		139,809
Actual, Ratio		19.13%
Minimum capital requirement, Amount		29,237
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		43,855
Well capitalized requirement, Ratio		6.00%
Tier 1 capital (to average assets)
Actual, Amount		139,809
Actual, Ratio		12.81%
Minimum capital requirement, Amount		43,660
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		54,575
Well capitalized requirement, Amount		5.00%
First Security Bank of Missoula [Member]
Total capital (to risk-weighted assets)
Actual, Amount		121,181
Actual, Ratio		17.18%
Minimum capital requirement, Amount		56,414
Minimum capital requirement, Ratio		8.00%
Well capitalized requirement, Amount		70,517
Well capitalized requirement, Ratio		10.00%
Tier 1 capital (to risk-weighted assets)
Actual, Amount		112,198
Actual, Ratio		15.91%
Minimum capital requirement, Amount		28,207
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		42,310
Well capitalized requirement, Ratio		6.00%
Tier 1 capital (to average assets)
Actual, Amount		112,198
Actual, Ratio		10.49%
Minimum capital requirement, Amount		42,793
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		53,492
Well capitalized requirement, Amount		5.00%
Western Security Bank [Member]
Total capital (to risk-weighted assets)
Actual, Amount		69,646
Actual, Ratio		17.07%
Minimum capital requirement, Amount		32,632
Minimum capital requirement, Ratio		8.00%
Well capitalized requirement, Amount		40,790
Well capitalized requirement, Ratio		10.00%
Tier 1 capital (to risk-weighted assets)
Actual, Amount		64,520
Actual, Ratio		15.82%
Minimum capital requirement, Amount		16,316
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		24,474
Well capitalized requirement, Ratio		6.00%
Tier 1 capital (to average assets)
Actual, Amount		64,520
Actual, Ratio		8.28%
Minimum capital requirement, Amount		31,159
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		38,949
Well capitalized requirement, Amount		5.00%
1st Bank [Member]
Total capital (to risk-weighted assets)
Actual, Amount		68,729
Actual, Ratio		19.48%
Minimum capital requirement, Amount		28,225
Minimum capital requirement, Ratio		8.00%
Well capitalized requirement, Amount		35,282
Well capitalized requirement, Ratio		10.00%
Tier 1 capital (to risk-weighted assets)
Actual, Amount		64,267
Actual, Ratio		18.22%
Minimum capital requirement, Amount		14,113
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		21,169
Well capitalized requirement, Ratio		6.00%
Tier 1 capital (to average assets)
Actual, Amount		64,267
Actual, Ratio		8.49%
Minimum capital requirement, Amount		30,279
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		37,849
Well capitalized requirement, Amount		5.00%
Valley Bank of Helena [Member]
Total capital (to risk-weighted assets)
Actual, Amount		34,117
Actual, Ratio		14.01%
Minimum capital requirement, Amount		19,476
Minimum capital requirement, Ratio		8.00%
Well capitalized requirement, Amount		24,345
Well capitalized requirement, Ratio		10.00%
Tier 1 capital (to risk-weighted assets)
Actual, Amount		31,059
Actual, Ratio		12.76%
Minimum capital requirement, Amount		9,738
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		14,607
Well capitalized requirement, Ratio		6.00%
Tier 1 capital (to average assets)
Actual, Amount		31,059
Actual, Ratio		6.94%
Minimum capital requirement, Amount		17,906
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		22,382
Well capitalized requirement, Amount		5.00%
Big Sky Western Bank [Member]
Total capital (to risk-weighted assets)
Actual, Amount		68,661
Actual, Ratio		25.43%
Minimum capital requirement, Amount		21,601
Minimum capital requirement, Ratio		8.00%
Well capitalized requirement, Amount		27,002
Well capitalized requirement, Ratio		10.00%
Tier 1 capital (to risk-weighted assets)
Actual, Amount		65,218
Actual, Ratio		24.15%
Minimum capital requirement, Amount		10,801
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		16,201
Well capitalized requirement, Ratio		6.00%
Tier 1 capital (to average assets)
Actual, Amount		65,218
Actual, Ratio		17.33%
Minimum capital requirement, Amount		15,057
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		18,821
Well capitalized requirement, Amount		5.00%
First Bank of Wyoming [Member]
Total capital (to risk-weighted assets)
Actual, Amount		41,860
Actual, Ratio		19.95%
Minimum capital requirement, Amount		16,789
Minimum capital requirement, Ratio		8.00%
Well capitalized requirement, Amount		20,987
Well capitalized requirement, Ratio		10.00%
Tier 1 capital (to risk-weighted assets)
Actual, Amount		39,670
Actual, Ratio		18.90%
Minimum capital requirement, Amount		8,395
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		12,592
Well capitalized requirement, Ratio		6.00%
Tier 1 capital (to average assets)
Actual, Amount		39,670
Actual, Ratio		10.40%
Minimum capital requirement, Amount		15,264
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		19,080
Well capitalized requirement, Amount		5.00%
Citizens Community Bank [Member]
Total capital (to risk-weighted assets)
Actual, Amount		29,011
Actual, Ratio		13.85%
Minimum capital requirement, Amount		16,763
Minimum capital requirement, Ratio		8.00%
Well capitalized requirement, Amount		20,954
Well capitalized requirement, Ratio		10.00%
Tier 1 capital (to risk-weighted assets)
Actual, Amount		26,358
Actual, Ratio		12.58%
Minimum capital requirement, Amount		8,382
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		12,572
Well capitalized requirement, Ratio		6.00%
Tier 1 capital (to average assets)
Actual, Amount		26,358
Actual, Ratio		7.65%
Minimum capital requirement, Amount		13,783
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		17,228
Well capitalized requirement, Amount		5.00%
First Bank of Montana [Member]
Total capital (to risk-weighted assets)
Actual, Amount		22,757
Actual, Ratio		15.05%
Minimum capital requirement, Amount		12,100
Minimum capital requirement, Ratio		8.00%
Well capitalized requirement, Amount		15,124
Well capitalized requirement, Ratio		10.00%
Tier 1 capital (to risk-weighted assets)
Actual, Amount		20,854
Actual, Ratio		13.79%
Minimum capital requirement, Amount		6,050
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		9,075
Well capitalized requirement, Ratio		6.00%
Tier 1 capital (to average assets)
Actual, Amount		20,854
Actual, Ratio		8.33%
Minimum capital requirement, Amount		10,008
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		12,510
Well capitalized requirement, Amount		5.00%
Bank of the San Juans [Member]
Total capital (to risk-weighted assets)
Actual, Amount		21,127
Actual, Ratio		13.63%
Minimum capital requirement, Amount		12,402
Minimum capital requirement, Ratio		8.00%
Well capitalized requirement, Amount		15,503
Well capitalized requirement, Ratio		10.00%
Tier 1 capital (to risk-weighted assets)
Actual, Amount		19,161
Actual, Ratio		12.36%
Minimum capital requirement, Amount		6,201
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		9,302
Well capitalized requirement, Ratio		6.00%
Tier 1 capital (to average assets)
Actual, Amount		19,161
Actual, Ratio		8.48%
Minimum capital requirement, Amount		9,042
Minimum capital requirement, Ratio		4.00%
Well capitalized requirement, Amount		$ 11,303
Well capitalized requirement, Amount		5.00%