Parent Company Financial Information - Statements of Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Dividend income:
Total dividend income	$ 7,186	$ 10,555	$ 0
Other income/(loss)	110,958	75,809	43,917
Provision/(provision credit) for loan losses	47,000	7,000	0
Interest expense:
Interest on term borrowings	53,263	53,047	36,037
Total interest expense	414,153	325,704	147,616
Compensation, employee benefits and other expense	695,351	658,223	587,465
Income/(loss) before income taxes	585,664	714,109	308,872
Income tax(benefit)/expense	133,291	157,602	131,892
Equity in undistributed net income/(loss) of subsidiaries:
Net income/(loss) attributable to controlling interest	440,908	545,042	165,515
Parent Company
Dividend income:
Bank	345,000	420,000	250,000
Non-bank	756	1,386	1,097
Total dividend income	345,756	421,386	251,097
Interest income	76	29	0
Other income/(loss)	965	83	190
Total income	346,797	421,498	251,287
Provision/(provision credit) for loan losses	(925)	0	0
Interest expense:
Interest on term borrowings	31,224	31,315	17,936
Total interest expense	31,224	31,315	17,936
Compensation, employee benefits and other expense	52,447	53,401	43,783
Total expense	82,746	84,716	61,719
Income/(loss) before income taxes	264,051	336,782	189,568
Income tax(benefit)/expense	(19,285)	(38,509)	512
Income/(loss) before equity in undistributed net income of subsidiaries	283,336	375,291	189,056
Equity in undistributed net income/(loss) of subsidiaries:
Bank	160,257	170,939	(24,255)
Non-bank	(2,685)	(1,188)	714
Net income/(loss) attributable to controlling interest	$ 440,908	$ 545,042	$ 165,515