Other Comprehensive Income (Loss) - Changes in the Components of Other Comprehensive Income (Loss), Net of Tax (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive income (loss), pre-tax	$ (3,429)	$ 3,980	$ (12,800)	$ 8,862
Total other comprehensive income (loss), tax expense (benefit)	(873)	1,538	(3,259)	3,426
Other comprehensive (loss) income, net of tax	(2,556)	2,442	(9,541)	5,436
Securities available for sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax	(4,025)	4,188	(14,634)	8,927
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	(1,025)	1,619	(3,725)	3,451
Other comprehensive income (loss), before reclassifications, net of tax	(3,000)	2,569	(10,909)	5,476
Reclassification from AOCI, pre-tax		(29)
Reclassification from AOCI, tax expense (benefit)		(11)
Reclassification from AOCI, net of tax		(18)
Total other comprehensive income (loss), pre-tax	(4,025)	4,159	(14,634)	8,652
Total other comprehensive income (loss), tax expense (benefit)	(1,025)	1,608	(3,725)	3,345
Other comprehensive (loss) income, net of tax	(3,000)	2,551	(10,909)	5,307
Derivative instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax	519	(270)	1,670	6
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	132	(105)	425	2
Other comprehensive income (loss), before reclassifications, net of tax	387	(165)	1,245	4
Total other comprehensive income (loss), pre-tax	519	(270)	1,670	6
Total other comprehensive income (loss), tax expense (benefit)	132	(105)	425	2
Other comprehensive (loss) income, net of tax	387	(165)	1,245	4
Defined benefit Pension and Post-Retirement Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive income (loss), pre-tax	77	91	164	204
Total other comprehensive income (loss), tax expense (benefit)	20	35	41	79
Other comprehensive (loss) income, net of tax	57	56	123	125
Amortization of net actuarial loss recognized in net periodic pension cost
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, pre-tax	77	91	164	204
Reclassification from AOCI, tax expense (benefit)	20	35	41	79
Reclassification from AOCI, net of tax	$ 57	$ 56	$ 123	125
Accumulated net investment gain (loss), amortization of unrealized holding gains transferred to held to maturity attributable to parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, pre-tax				(275)
Reclassification from AOCI, tax expense (benefit)				(106)
Reclassification from AOCI, net of tax				$ (169)