Accumulated Other Comprehensive Income (Loss) - Reclassifications out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Reclassifications out of accumulated other comprehensive income, net of tax
Interest expense	$ (22,628)	$ (15,271)	$ (65,554)	$ (36,516)
Provision for income taxes	(12,998)	(9,823)	(34,455)	(32,752)
Net income	51,565	47,082	137,392	129,867
Amount Reclassified from Accumulated Other Comprehensive Loss
Reclassifications out of accumulated other comprehensive income, net of tax
Net income	(529)	187	7,785	1,055
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	(241)	35	(585)	121
Provision for income taxes	53	(8)	128	(27)
Net income	(188)	27	(457)	94
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	(437)	11	2,679	652
Provision for income taxes	96	(2)	(590)	(144)
Net income	$ (341)	9	2,089	508
Benefit Plans | Amount Reclassified from Accumulated Other Comprehensive Loss
Reclassifications out of accumulated other comprehensive income, net of tax
Salaries and employee benefits		194	7,888	581
Provision for income taxes		(43)	(1,735)	(128)
Net income		$ 151	$ 6,153	$ 453