Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net Income	$ 17,478	$ 12,234	$ 33,248	$ 25,123
Net change in unrealized gains (losses) on investment securities available-for-sale
Net unrealized gains (losses) arising during the period, net of tax expense (benefit) of $2,870, $(3,692), $9,350 and ($893), respectively	4,683	(6,024)	15,255	(1,457)
Less: reclassification adjustment for net gains on sales realized in net income, net of tax expense of $207, $181, $323 and $352, respectively	(338)	(296)	(527)	(576)
Net change in unrealized gains (losses) on investment securities available-for-sale	4,345	(6,320)	14,728	(2,033)
Net change in securities held-to-maturity
Amortization of unrealized gain on securities reclassified to held-to-maturity, net of tax ( benefit) of $62, $120, $127, $120, respectively	(100)	(37)	(203)	(208)
Net change in unfunded pension liability
Change in unfunded pension liability related to unrealized (loss) gain, prior service cost and transition obligation, net of tax (benefit) expense of ($13), ($9), $280 and ($18), respectively	(22)	(15)	456	(30)
Total other comprehensive (loss) income	4,223	(6,372)	14,981	(2,271)
Total comprehensive income	$ 21,701	$ 5,862	$ 48,229	$ 22,852