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, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive income (loss), pre-tax	$ 1,587			$ (5,594)			$ 26,276	$ (18,394)
Total other comprehensive income (loss), tax expense (benefit)	403			(1,423)			6,686	(4,682)
Other comprehensive income (loss), net of tax	1,184	$ 7,960	$ 10,446	(4,171)	$ (2,556)	$ (6,985)	19,590	(13,712)
Securities available for sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax	(84)			(6,548)			27,695	(21,182)
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	(22)			(1,666)			7,047	(5,391)
Other comprehensive income (loss), before reclassifications, net of tax	(62)			(4,882)			20,648	(15,791)
Reclassification from AOCI, pre-tax	2,516			15			2,511	15
Reclassification from AOCI, tax expense (benefit)	640			4			639	4
Reclassification from AOCI, net of tax	1,876			11			1,872	11
Total other comprehensive income (loss), pre-tax	2,432			(6,533)			30,206	(21,167)
Total other comprehensive income (loss), tax expense (benefit)	618			(1,662)			7,686	(5,387)
Other comprehensive income (loss), net of tax	1,814			(4,871)			22,520	(15,780)
Derivative instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax	(949)						(4,244)
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	(241)						(1,080)
Other comprehensive income (loss), before reclassifications, net of tax	(708)						(3,164)
Total other comprehensive income (loss), pre-tax	(949)						(4,244)
Total other comprehensive income (loss), tax expense (benefit)	(241)						(1,080)
Other comprehensive income (loss), net of tax	(708)						(3,164)
Amortization of net actuarial loss recognized in net periodic pension cost
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, pre-tax	104			82			314	246
Reclassification from AOCI, tax expense (benefit)	26			21			80	62
Reclassification from AOCI, net of tax	78			61			234	184
Defined benefit pension and post-retirement benefit plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive income (loss), pre-tax	104			82			314	246
Total other comprehensive income (loss), tax expense (benefit)	26			21			80	62
Other comprehensive income (loss), net of tax	$ 78			61			$ 234	184
Derivative instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax				857				2,527
Other comprehensive income (loss) before reclassifications, tax expense (benefit)				218				643
Other comprehensive income (loss), before reclassifications, net of tax				639				1,884
Total other comprehensive income (loss), pre-tax				857				2,527
Total other comprehensive income (loss), tax expense (benefit)				218				643
Other comprehensive income (loss), net of tax				$ 639				$ 1,884