CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income		$ 43,465	$ 40,824	$ 36,153
Securities available for sale:
Changes in fair value of securities available for sale		(3,171)	1,021	(6,696)
Net losses on securities classified into earnings		0	0	188	[1]
Net change in fair value of securities available for sale		(3,171)	1,021	(6,508)
Reclassification adjustment for other-than-temporary impairment losses transferred into earnings		0	0	1,937	[2]
Cash flow hedges:
Change in fair value of cash flow hedges		(53)	(38)	(35)
Net cash flow hedge losses reclassified into earnings	[3]	297	369	423
Net change in fair value of cash flow hedges		244	331	388
Defined benefit plan obligation adjustment	[4]	2,037	(8,608)	13,129
Total other comprehensive (loss) income, net of tax		(890)	(7,256)	8,946
Total comprehensive income		$ 42,575	$ 33,568	$ 45,099

[1] Reported as net realized gains on securities and 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.