Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Consolidated Statements of Comprehensive Income
Net income	$ 49,219	$ 30,032	$ 22,595
Unrealized gains on securities:
Unrealized holding gains (losses) arising during period	(23,069)	4,739	7,345
Tax effect	8,732	(1,793)	(2,647)
Reclassification adjustment for gains included in net income		(189)	(323)
Tax effect		72	126
Net of tax amount	(14,337)	2,829	4,501
Noncredit portion of other-than-temporary impairment losses:
Total other-than-temporary impairment losses			(115)
Tax effect			44
Reclassification adjustment of credit portion included in net income			115
Tax effect			(44)
Unrealized losses on derivative financial instruments qualifying as cash flow hedges:
Unrealized holding gains (losses) arising during period	283	(403)	(1,060)
Tax effect	(108)	153	428
Reclassification adjustment for losses included in interest expense	307	293	304
Tax effect	(117)	(112)	(123)
Net of tax amount	365	(69)	(451)
Change in pension and retiree medical plan obligation:
Change in pension and retiree medical plan obligation during period	5,804	139	(5,156)
Tax effect	(2,249)	(87)	2,119
Reclassification adjustment for actuarial losses included in salaries and employee benefits	482	471	45
Tax effect	(164)	(158)	(15)
Net of tax amount	3,873	365	(3,007)
Other comprehensive income, net of tax	(10,099)	3,125	1,043
Comprehensive income	$ 39,120	$ 33,157	$ 23,638