Accumulated Other Comprehensive Income (Loss) - Reclassifications out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Reclassifications out of accumulated other comprehensive income, net of tax
Interest expense	$ (18,007)	$ (22,803)	$ (37,793)	$ (42,926)
Other-than-temporary impairment losses			0
Provision for income taxes	24,747	(10,226)	20,492	(21,457)
Net income	(84,935)	41,460	(60,825)	85,827
Amount Reclassified from Accumulated Other Comprehensive Loss
Reclassifications out of accumulated other comprehensive income, net of tax
Net income	1,532	5,877	2,095	8,315
Losses on Cash Flow Hedges | Amount Reclassified from Accumulated Other Comprehensive Loss | Interest rate contracts
Reclassifications out of accumulated other comprehensive income, net of tax
Interest expense	1,964	(350)	2,686	(343)
Provision for income taxes	(432)	77	(591)	75
Net income	$ 1,532	(273)	$ 2,095	(268)
Losses on sales of available for sale securities: | Amount Reclassified from Accumulated Other Comprehensive Loss
Reclassifications out of accumulated other comprehensive income, net of tax
Securities (gains) losses, net		118		3,116
Provision for income taxes		(26)		(686)
Net income		92		2,430
Benefit Plans | Amount Reclassified from Accumulated Other Comprehensive Loss
Reclassifications out of accumulated other comprehensive income, net of tax
Salaries and employee benefits /Pension Plan Termination Expense		7,767		7,888
Provision for income taxes		(1,709)		(1,735)
Net income		$ 6,058		$ 6,153