Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net Income	$ 20,570	$ 17,478	$ 39,507	$ 33,248
Net change in unrealized gains on investment securities available for sale
Net unrealized gains arising during the period, net of tax expense of $1,958, $2,870, $2,737 and $9,350, respectively	3,241	4,683	4,513	15,255
Less: reclassification adjustment for net gains on sales realized in net income, net of tax expense of $253, $207, $367 and $323, respectively	(455)	(338)	(661)	(527)
Net change in unrealized gains (losses) on investment securities available-for-sale	2,786	4,345	3,852	14,728
Net change in securities held to maturity
Amortization of unrealized gain on securities reclassified to held-to-maturity, net of tax expense of $62, $62, $121 and $127, respectively	(97)	(100)	(198)	(203)
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 ($15), ($13), ($27) and $280, respectively	(22)	(22)	(45)	456
Net change in cash flow hedge
Net unrealized gain arising during the period, net of tax expense of $161, $0, $92 and $0, respectively	262	0	150	0
Total other comprehensive income	2,929	4,223	3,759	14,981
Total comprehensive income	$ 23,499	$ 21,701	$ 43,266	$ 48,229