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, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive income (loss), pre-tax	$ (9,371)	$ 4,882
Total other comprehensive income (loss), tax expense (benefit)	(2,386)	1,888
Other comprehensive (loss) income, net of tax	(6,985)	2,994
Securities available for sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax	(10,609)	4,739
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	(2,700)	1,832
Other comprehensive income (loss), before reclassifications, net of tax	(7,909)	2,907
Reclassification from AOCI, pre-tax		(246)
Reclassification from AOCI, tax expense (benefit)		(95)
Reclassification from AOCI, net of tax		(151)
Total other comprehensive income (loss), pre-tax	(10,609)	4,493
Total other comprehensive income (loss), tax expense (benefit)	(2,700)	1,737
Other comprehensive (loss) income, net of tax	(7,909)	2,756
Derivative instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax	1,151	276
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	293	107
Other comprehensive income (loss), before reclassifications, net of tax	858	169
Total other comprehensive income (loss), pre-tax	1,151	276
Total other comprehensive income (loss), tax expense (benefit)	293	107
Other comprehensive (loss) income, net of tax	858	169
Defined benefit Pension and Post-Retirement Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive income (loss), pre-tax	87	113
Total other comprehensive income (loss), tax expense (benefit)	21	44
Other comprehensive (loss) income, net of tax	66	69
Amortization of net actuarial loss recognized in net periodic pension cost
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, pre-tax	87	113
Reclassification from AOCI, tax expense (benefit)	21	44
Reclassification from AOCI, net of tax	$ 66	$ 69