Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net Income	$ 18,937	$ 15,770
Net change in unrealized gains on investment securities available for sale
Net unrealized gains arising during the period, net of tax expense of $779 and $6,479, respectively	1,272	10,572
Less: reclassification adjustment for net gains on sales realized in net income, net of tax expense of $114 and $116, respectively	(206)	(189)
Net change in unrealized gains (losses) on investment securities available-for-sale	1,066	10,383
Net change in securities held to maturity
Amortization of unrealized gain on securities reclassified to held-to-maturity, net of tax expense of $59 and $65, respectively	(101)	(103)
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 ($12) and $306, respectively	(23)	478
Net change in cash flow hedge
Net unrealized loss arising during the period, net of tax benefit of ($69) and $0, respectively	(112)	0
Total other comprehensive income	830	10,758
Total comprehensive income	$ 19,767	$ 26,528