Accumulated Other Comprehensive Income (Loss) - Reclassifications out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Reclassifications out of accumulated other comprehensive income, net of tax
Interest expense	$ (22,803)	$ (12,170)	$ (42,926)	$ (21,245)
Provision for income taxes	(10,226)	(11,644)	(21,457)	(22,929)
Net income	41,460	40,459	85,827	82,785
Amount Reclassified from Accumulated Other Comprehensive Loss
Reclassifications out of accumulated other comprehensive income, net of tax
Net income	4,452	682	4,131	870
Gains and 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	(350)	39	(343)	87
Provision for income taxes	77	(8)	75	(19)
Net income	(273)	31	(268)	68
Unrealized Gains and Losses on Securities Available for Sale | Amount Reclassified from Accumulated Other Comprehensive Loss
Reclassifications out of accumulated other comprehensive income, net of tax
Securities (gains) losses, net	(1,709)	641	(2,250)	641
Provision for income taxes	376	(141)	496	(141)
Net income	(1,333)	500	(1,754)	500
Benefit Plans | Amount Reclassified from Accumulated Other Comprehensive Loss
Reclassifications out of accumulated other comprehensive income, net of tax
Salaries and employee benefits	7,767	194	7,888	387
Provision for income taxes	(1,709)	(43)	(1,735)	(85)
Net income	$ 6,058	$ 151	$ 6,153	$ 302