Accumulated Other Comprehensive Loss - Reclassifications from AOCI (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
Reclassification Out Of Accumulated Other Comprehensive Loss
Losses on securities transactions, net	$ (93)			$ (79)			$ (114)	$ (880)
Tax effect	(25,307)			(18,046)			(110,035)	(50,191)
Total net of tax	81,891	$ 76,468	$ 113,330	69,559	$ 72,802	$ 41,965	271,689	184,326
Interest expense	(108,636)			(80,241)			(317,720)	(209,504)
Total reclassifications, net of tax	(452)			(642)			(1,062)	(3,095)
Unrealized gains (losses) on AFS securities before tax
Reclassification Out Of Accumulated Other Comprehensive Loss
Total reclassifications, net of tax	(72)						(90)
Unrealized losses on derivatives (cash flow hedges) before tax
Reclassification Out Of Accumulated Other Comprehensive Loss
Total reclassifications, net of tax	(324)						(806)
Defined Benefit Pension Plan
Reclassification Out Of Accumulated Other Comprehensive Loss
Amortization of net loss	(79)			(157)			(235)	(471)
Tax effect	23			44			69	134
Total reclassifications, net of tax	(56)			(113)			(166)	(337)
Reclassification Out of Accumulated Other Comprehensive Income (Loss)
Reclassification Out Of Accumulated Other Comprehensive Loss
Interest expense	(453)			(660)			(1,126)	(2,977)
Reclassification Out of Accumulated Other Comprehensive Income (Loss) | Unrealized gains (losses) on AFS securities before tax
Reclassification Out Of Accumulated Other Comprehensive Loss
Losses on securities transactions, net	(93)			(86)			(114)	(881)
Tax effect	21			29			24	250
Total net of tax	(72)			(57)			(90)	(631)
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	129			188			320	850
Total net of tax	(324)			(472)			(806)	(2,127)
Interest expense	$ (453)			$ (660)			$ (1,126)	$ (2,977)