CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 10,391	$ 10,379
Unrealized gains and losses on securities:
Unrealized holding gains on available-for-sale securities arising during the period	895	1,509
Tax effect	(357)	(595)
Net of tax	$ 538	914
Reclassification adjustment for realized gains included in net income		(506)
Tax effect		207
Net of tax		(299)
Amortization of unrealized net losses on held-to-maturity securities transferred from available-for-sale securities	$ 51	65
Tax effect	(20)	(25)
Net of tax	31	40
Unrealized losses on cash flow hedge	(1,437)	(534)
Tax effect	587	218
Net of tax	(850)	(316)
Unrealized pension plan (losses) gains before reclassifications	$ (1)	634
Tax effect		(259)
Net of tax	$ (1)	375
Reclassification adjustment for realized losses included in net income	102	108
Tax effect	(41)	(44)
Net of tax	61	64
Total other comprehensive (loss) income	(221)	778
Total comprehensive income	$ 10,170	$ 11,157