CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net change in Unrealized (losses) gains, tax (benefit) expense	$ 3,714	$ 779
Reclassification adjustment for gains, tax expense	5	114
Amortization of unrealized gain on securities reclassified to held-to-maturity, tax expense	37	59
Change in unfunded pension liability related to unrealized (loss) gain, prior service cost and transition obligation, tax (benefit) expense	(11)	(12)
Reclassification adjustment related to derivatives, tax benefit (expense)	$ (240)	$ (69)