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, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive income (loss), pre-tax	$ 10,677		$ (3,429)		$ 24,690	$ (12,800)
Total other comprehensive income (loss), tax expense (benefit)	2,717		(873)		6,284	(3,259)
Other comprehensive income (loss), net of tax	7,960	$ 10,446	(2,556)	$ (6,985)	18,406	(9,541)
Securities available for sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax	12,599				27,780	(14,634)
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	3,206				7,070	(3,725)
Other comprehensive income (loss), before reclassifications, net of tax	9,393				20,710	(10,909)
Reclassification from AOCI, pre-tax	8				(5)
Reclassification from AOCI, tax expense (benefit)	2				(1)
Reclassification from AOCI, net of tax	6				(4)
Total other comprehensive income (loss), pre-tax	12,607		(4,025)		27,775	(14,634)
Total other comprehensive income (loss), tax expense (benefit)	3,208		(1,025)		7,069	(3,725)
Other comprehensive income (loss), net of tax	9,399		(3,000)		20,706	(10,909)
Derivative Instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax	(2,067)				(3,294)
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	(526)				(838)
Other comprehensive income (loss), before reclassifications, net of tax	(1,541)				(2,456)
Total other comprehensive income (loss), pre-tax	(2,067)				(3,294)
Total other comprehensive income (loss), tax expense (benefit)	(526)				(838)
Other comprehensive income (loss), net of tax	(1,541)				(2,456)
Derivative instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax			519			1,670
Other comprehensive income (loss) before reclassifications, tax expense (benefit)			132			425
Other comprehensive income (loss), before reclassifications, net of tax			387			1,245
Total other comprehensive income (loss), pre-tax			519			1,670
Total other comprehensive income (loss), tax expense (benefit)			132			425
Other comprehensive income (loss), net of tax			387			1,245
Amortization of net actuarial loss recognized in net periodic pension cost
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, pre-tax	137		77		209	164
Reclassification from AOCI, tax expense (benefit)	35		20		53	41
Reclassification from AOCI, net of tax	102		57		156	123
Defined benefit Pension and Post-Retirement Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive income (loss), pre-tax	137		77		209	164
Total other comprehensive income (loss), tax expense (benefit)	35		20		53	41
Other comprehensive income (loss), net of tax	$ 102		57		$ 156	$ 123
Unrealized holding losses on securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax			(4,025)
Other comprehensive income (loss) before reclassifications, tax expense (benefit)			(1,025)
Other comprehensive income (loss), before reclassifications, net of tax			$ (3,000)