Accumulated Other Comprehensive Income (Loss) - Amounts Reclassified Out of Accumulated Other Comprehensive Income (Loss) (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
Other interest expense	$ (16,055)		$ (29,566)		$ (41,899)	$ (57,576)
Other operating expense	(3,609)		(3,338)		(7,920)	(7,965)
Total before tax	24,080		13,828		22,484	23,183
Tax expense (benefit)	(5,808)		(3,272)		(5,602)	(5,559)
Net income	18,272	$ (1,390)	10,556	$ 7,068	16,882	17,624
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Net loss on sale of securities	(54)		(15)		(91)	(15)
Tax expense (benefit)	17		5		29	5
Net income	(37)		(10)		(62)	(10)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Tax expense (benefit)	182		(200)
Net income	(399)		447
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] | Interest Rate Swap [Member]
Other interest expense	(581)		647		(789)	848
Tax expense (benefit)					247	(262)
Net income					(542)	(586)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Other operating expense	(98)		(31)		(195)	(63)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Other operating expense	23		20		43	42
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Total before tax	(75)		(11)		(152)	(21)
Tax expense (benefit)	23		3		47	6
Net income	$ (52)		$ (8)		$ (105)	$ (15)