CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net Income	$ 37,350	$ 18,937
Net change in unrealized (loss) gains on investment securities available for sale
Net unrealized (loss) gains arising during the period, net of tax expense of $3,714 and $779, respectively	(11,827)	1,272
Less: reclassification adjustment for net gains on sales realized in net income, net of tax expense of $5 and $114, respectively	(16)	(206)
Net change in unrealized gains (losses) on investment securities available-for-sale	(11,843)	1,066
Net change in securities held to maturity
Amortization of unrealized gain on securities reclassified to held-to-maturity, net of tax expense of $37 and $59, respectively	(119)	(101)
Net change in unfunded pension liability
Change in unfunded pension liability related to unrealized gain (loss), prior service cost and transition obligation, net of tax benefit of ($11) and ($12), respectively	59	(23)
Net change in cash flow hedge
Net unrealized loss arising during the period, net of tax benefit of ($240) and ($69), respectively	(765)	(112)
Total other comprehensive (loss) income	(12,668)	830
Total comprehensive income	$ 24,682	$ 19,767