Other Comprehensive Income - Changes in the Components of Other Comprehensive Income (Loss), Net of Tax (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive income (loss), pre-tax	$ 2,469		$ 10,677		$ 20,892	$ 24,690
Total other comprehensive income (loss), tax expense (benefit)	631		2,717		5,317	6,284
Other comprehensive income, net of tax	1,838	$ 13,737	7,960	$ 10,446	15,575	18,406
Securities available for sale:
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax	3,496		12,599		25,885	27,780
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	893		3,206		6,588	7,070
Other comprehensive income (loss), before reclassifications, net of tax	2,603		9,393		19,297	20,710
Reclassification from AOCI, pre-tax			8		(31)	(5)
Reclassification from AOCI, tax expense (benefit)			2		(8)	(1)
Reclassification from AOCI, net of tax			6		(23)	(4)
Total other comprehensive income (loss), pre-tax	3,465		12,607		25,854	27,775
Total other comprehensive income (loss), tax expense (benefit)	885		3,208		6,580	7,069
Other comprehensive income, net of tax	2,580		9,399		19,274	20,706
Derivative instruments:
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax	(1,064)				(5,092)	(3,294)
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	(271)				(1,296)	(838)
Other comprehensive income (loss), before reclassifications, net of tax	(793)				(3,796)	(2,456)
Total other comprehensive income (loss), pre-tax	(1,064)				(5,092)	(3,294)
Total other comprehensive income (loss), tax expense (benefit)	(271)				(1,296)	(838)
Other comprehensive income, net of tax	(793)				(3,796)	(2,456)
Amortization of net actuarial loss recognized in net periodic pension cost
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, pre-tax	68		137		130	209
Reclassification from AOCI, tax expense (benefit)	17		35		33	53
Reclassification from AOCI, net of tax	51		102		97	156
Total defined benefit pension and post-retirement benefit plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive income (loss), pre-tax	68		137		130	209
Total other comprehensive income (loss), tax expense (benefit)	17		35		33	53
Other comprehensive income, net of tax	$ 51		102		$ 97	$ 156
Derivative instruments:
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax			(2,067)
Other comprehensive income (loss) before reclassifications, tax expense (benefit)			(526)
Other comprehensive income (loss), before reclassifications, net of tax			(1,541)
Total other comprehensive income (loss), pre-tax			(2,067)
Total other comprehensive income (loss), tax expense (benefit)			(526)
Other comprehensive income, net of tax			$ (1,541)