Consideration Transferred, Identifiable Net Assets Acquired and Goodwill Recognized (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Fair value of consideration transferred
Fair value of Company shares issued, net of equity issuance costs			$ 45,033
Cash consideration for outstanding shares			24,858
Total fair value of consideration transferred			69,891
Identifiable assets acquired
Cash and cash equivalents	51,013		51,013
Investment securities, available-for-sale	123,701		123,701
Loans receivable	387,185		387,185
Core deposit intangible	5,739		5,739
Accrued income and other assets	39,325		39,325
Total identifiable assets acquired	606,963		606,963
Liabilities assumed
Deposits	550,177		550,177
Federal Home Loan Bank advances and other borrowed funds	5,467		5,467
Accrued expenses and other liabilities	5,034		5,034
Total liabilities assumed	560,678		560,678
Total identifiable net assets	46,285		46,285
Goodwill recognized	10,197	0	23,606	0
Wheatland Bankshares
Fair value of consideration transferred
Fair value of Company shares issued, net of equity issuance costs			28,290
Cash consideration for outstanding shares			11,025
Total fair value of consideration transferred			39,315
Identifiable assets acquired
Cash and cash equivalents	23,148		23,148
Investment securities, available-for-sale	75,643		75,643
Loans receivable	171,199		171,199
Core deposit intangible	2,079		2,079
Accrued income and other assets	15,063		15,063
Total identifiable assets acquired	287,132		287,132
Liabilities assumed
Deposits	255,197		255,197
Federal Home Loan Bank advances and other borrowed funds	5,467		5,467
Accrued expenses and other liabilities	562		562
Total liabilities assumed	261,226		261,226
Total identifiable net assets	25,906		25,906
Goodwill recognized			13,409
North Cascades Bancshares
Fair value of consideration transferred
Fair value of Company shares issued, net of equity issuance costs			16,743
Cash consideration for outstanding shares			13,833
Total fair value of consideration transferred			30,576
Identifiable assets acquired
Cash and cash equivalents	27,865		27,865
Investment securities, available-for-sale	48,058		48,058
Loans receivable	215,986		215,986
Core deposit intangible	3,660		3,660
Accrued income and other assets	24,262		24,262
Total identifiable assets acquired	319,831		319,831
Liabilities assumed
Deposits	294,980		294,980
Federal Home Loan Bank advances and other borrowed funds	0		0
Accrued expenses and other liabilities	4,472		4,472
Total liabilities assumed	299,452		299,452
Total identifiable net assets	20,379		20,379
Goodwill recognized			$ 10,197