Consideration Transferred, Identifiable Net Assets Acquired and Goodwill Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Liabilities assumed
Goodwill recognized	$ 10,932	$ 0	$ 23,606
Bargain purchase gain	0	(680)	$ 0
Canon National Bank
Fair value of consideration transferred
Fair value of Company shares issued, net of equity issuance costs	15,163
Cash consideration for outstanding shares	16,145
Contingent consideration	0
Total fair value of consideration transferred	31,308
Identifiable assets acquired
Cash and cash equivalents	17,860
Investment securities	68,486
Loans receivable	159,759
Core deposit intangible	4,532
Accrued income and other assets	9,689
Total identifiable assets acquired	260,326
Liabilities assumed
Deposits	237,326
FHLB advances and repurchase agreements	0
Accrued expenses and other liabilities	1,487
Total liabilities assumed	238,813
Total identifiable net assets	21,513
Goodwill recognized	9,795
Montana Community Banks, Inc.
Fair value of consideration transferred
Fair value of Company shares issued, net of equity issuance costs	10,776
Cash consideration for outstanding shares	12,219
Contingent consideration	0
Total fair value of consideration transferred	22,995
Identifiable assets acquired
Cash and cash equivalents	31,931
Investment securities	42,350
Loans receivable	84,689
Core deposit intangible	2,087
Accrued income and other assets	13,580
Total identifiable assets acquired	174,637
Liabilities assumed
Deposits	146,820
FHLB advances and repurchase agreements	3,292
Accrued expenses and other liabilities	2,667
Total liabilities assumed	152,779
Total identifiable net assets	21,858
Goodwill recognized	$ 1,137
FNBR Holding Corporation
Fair value of consideration transferred
Fair value of Company shares issued, net of equity issuance costs		15,127
Cash consideration for outstanding shares		16,690
Contingent consideration		0
Total fair value of consideration transferred		31,817
Identifiable assets acquired
Cash and cash equivalents		14,578
Investment securities		157,018
Loans receivable		137,488
Core deposit intangible		4,199
Accrued income and other assets		35,884
Total identifiable assets acquired		349,167
Liabilities assumed
Deposits		309,641
FHLB advances and repurchase agreements		0
Accrued expenses and other liabilities		7,029
Total liabilities assumed		316,670
Total identifiable net assets		32,497
Bargain purchase gain		$ (680)