Other Comprehensive Income (Loss) - Changes in the Components of Other Comprehensive Income (Loss), Net of Tax (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive income (loss), pre-tax	$ 12,230	$ 2,788	$ 21,092	$ 5,326
Total other comprehensive income (loss), tax expense (benefit)	4,728	1,078	8,154	2,049
Other comprehensive income, net of tax	7,502	1,710	12,938	3,277
Securities available for sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax	(1,245)	2,258	7,682	8,573
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	(481)	873	2,970	3,313
Other comprehensive income (loss), before reclassifications, net of tax	(764)	1,385	4,712	5,260
Total other comprehensive income (loss), pre-tax	11,966	2,240	20,618	7,308
Total other comprehensive income (loss), tax expense (benefit)	4,626	866	7,971	2,825
Other comprehensive income, net of tax	7,340	1,374	12,647	4,483
Unrealized holding gains on securities transfered from held to maturity to available for sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax	13,218		13,218
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	5,110		5,110
Other comprehensive income (loss), before reclassifications, net of tax	8,108		8,108
Securities available for sale, amortization of gains transferred to held to maturity
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, pre-tax	(7)	(18)	(282)	(79)
Reclassification from AOCI, tax expense (benefit)	(3)	(7)	(109)	(30)
Reclassification from AOCI, net of tax	(4)	(11)	(173)	(49)
Derivative instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax	163	807	169	(1,959)
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	63	312	65	(760)
Other comprehensive income (loss), before reclassifications, net of tax	100	495	104	(1,199)
Total other comprehensive income (loss), pre-tax	163	807	169	(1,959)
Total other comprehensive income (loss), tax expense (benefit)	63	312	65	(760)
Other comprehensive income, net of tax	100	495	104	(1,199)
Securities available for sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, pre-tax				(1,186)
Reclassification from AOCI, tax expense (benefit)				(458)
Reclassification from AOCI, net of tax				(728)
Defined benefit Pension and Post-Retirement Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive income (loss), pre-tax	101	(259)	305	(23)
Total other comprehensive income (loss), tax expense (benefit)	39	(100)	118	(16)
Other comprehensive income, net of tax	62	(159)	187	(7)
Net settlement gain (loss) attributable to parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, pre-tax		(383)		(383)
Reclassification from AOCI, tax expense (benefit)		(148)		(148)
Reclassification from AOCI, net of tax		(235)		(235)
Amortization of net actuarial loss recognized in net periodic pension cost
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, pre-tax	101	124	305	360
Reclassification from AOCI, tax expense (benefit)	39	48	118	132
Reclassification from AOCI, net of tax	$ 62	$ 76	$ 187	$ 228