Accumulated Other Comprehensive Loss - Reclassifications from AOCI (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
Reclassification Out Of Accumulated Other Comprehensive Loss
Gains (losses) on securities transactions, net	$ 11		$ (36)		$ (21)	$ (801)
Tax effect	(27,532)		(18,961)		(84,728)	(32,145)
Total net of tax	76,468	$ 113,330	72,802	$ 41,965	189,798	114,767
Interest expense	(107,508)		(69,366)		(209,084)	(129,263)
Total reclassifications, net of tax	(321)		(773)		(610)	(2,453)
Unrealized gains (losses) on AFS securities before tax
Reclassification Out Of Accumulated Other Comprehensive Loss
Total reclassifications, net of tax	8				(18)
Unrealized losses on derivatives (cash flow hedges) before tax
Reclassification Out Of Accumulated Other Comprehensive Loss
Total reclassifications, net of tax	(274)				(482)
Defined Benefit Pension Plan
Reclassification Out Of Accumulated Other Comprehensive Loss
Amortization of net loss	(78)		(157)		(156)	(314)
Tax effect	23		45		46	90
Total reclassifications, net of tax	(55)		(112)		(110)	(224)
Reclassification Out of Accumulated Other Comprehensive Income (Loss)
Reclassification Out Of Accumulated Other Comprehensive Loss
Interest expense	(383)		(866)		(673)	(2,317)
Reclassification Out of Accumulated Other Comprehensive Income (Loss) | Unrealized gains (losses) on AFS securities before tax
Reclassification Out Of Accumulated Other Comprehensive Loss
Gains (losses) on securities transactions, net	11		(52)		(21)	(795)
Tax effect	(3)		10		3	221
Total net of tax	8		(42)		(18)	(574)
Reclassification Out of Accumulated Other Comprehensive Income (Loss) | Unrealized losses on derivatives (cash flow hedges) before tax
Reclassification Out Of Accumulated Other Comprehensive Loss
Tax effect	109		247		191	662
Total net of tax	(274)		(619)		(482)	(1,655)
Interest expense	$ (383)		$ (866)		$ (673)	$ (2,317)