Other Comprehensive Income (Loss) - Changes in the Components of Other Comprehensive Income (Loss), Net of Tax (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive income (loss), pre-tax	$ 14,010	$ (9,371)
Total other comprehensive income (loss), tax expense (benefit)	3,564	(2,386)
Other comprehensive income (loss), net of tax	10,446	(6,985)
Securities available for sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax	15,179
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	3,862
Other comprehensive income (loss), before reclassifications, net of tax	11,317
Reclassification from AOCI, pre-tax	(13)
Reclassification from AOCI, tax expense (benefit)	(3)
Reclassification from AOCI, net of tax	(10)
Total other comprehensive income (loss), pre-tax	15,166	(10,609)
Total other comprehensive income (loss), tax expense (benefit)	3,859	(2,700)
Other comprehensive income (loss), net of tax	11,307	(7,909)
Derivative instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax	(1,228)	1,151
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	(313)	293
Other comprehensive income (loss), before reclassifications, net of tax	(915)	858
Total other comprehensive income (loss), pre-tax	(1,228)	1,151
Total other comprehensive income (loss), tax expense (benefit)	(313)	293
Other comprehensive income (loss), net of tax	(915)	858
Amortization of net actuarial loss recognized in net periodic pension cost
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, pre-tax	72	87
Reclassification from AOCI, tax expense (benefit)	18	21
Reclassification from AOCI, net of tax	54	66
Defined benefit Pension and Post-Retirement Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive income (loss), pre-tax	72	87
Total other comprehensive income (loss), tax expense (benefit)	18	21
Other comprehensive income (loss), net of tax	$ 54	66
Unrealized holding losses on securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax		(10,609)
Other comprehensive income (loss) before reclassifications, tax expense (benefit)		(2,700)
Other comprehensive income (loss), before reclassifications, net of tax		$ (7,909)