CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Statement of Comprehensive Income [Abstract]
Net income	$ 36,153		$ 35,074		$ 29,724
Securities available for sale:
Changes in fair value of securities available for sale	(6,808)		(2,666)		1,622
Net losses (gains) on securities classified into earnings	188	[1]	(768)	[1]	(415)	[1]
Net change in fair value of securities available for sale	(6,620)		(3,434)		1,207
Reclassification adjustment for other-than-temporary impairment losses transferred into earnings	2,049	[2]	125	[2]	88	[2]
Cash flow hedges:
Change in fair value of cash flow hedges	(35)		(333)		(942)
Net cash flow hedge losses reclassified into earnings	423	[3]	454	[3]	486	[3]
Net change in fair value of cash flow hedges	388		121		(456)
Defined benefit plan obligation adjustment	13,129	[4]	(5,416)	[4]	(6,759)	[4]
Total other comprehensive income (loss), net of tax	8,946		(8,604)		(5,920)
Total comprehensive income	$ 45,099		$ 26,470		$ 23,804

[1] Reported as total other-than-temporary impairment losses on securities in the Consolidated Statements of Income.

[2] Reported as the portion of loss recognized in other comprehensive income in the Consolidated Statements of Income.

[3] Included in interest expense on junior subordinated debentures in the Consolidated Statements of Income.

[4] Included in salaries and employee benefits expense in the Consolidated Statements of Income.