Parent Company Information (Components of Condensed Income Statement The Parent Company) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Income:
Total operating income	$ 524,492	$ 483,633	$ 394,690
Operating Expense:
Compensation and benefits	395,402	381,496	356,505
Non-interest expense	98,617	91,046	90,626
Income tax benefit	(103,969)	(81,215)	(98,351)
Net income	382,723	360,418	255,439
Parent Company [Member]
Operating Income:
Dividend income from bank subsidiary	360,000	290,000	120,000
Interest on securities and deposits	10,728	7,342	4,477
Alternative investments income	(256)	290	1,504
Other non-interest income	382	805	204
Total operating income	370,854	298,437	126,185
Operating Expense:
Interest expense on borrowings	21,062	11,127	10,380
Non-interest expense	15,527	19,105	23,008
Total operating expense	36,589	30,232	33,388
Income before income tax benefit and equity in undistributed earnings of subsidiaries	334,265	268,205	92,797
Income tax benefit	4,671	2,207	3,004
Equity in undistributed earnings of subsidiaries	43,787	90,006	159,638
Net income	$ 382,723	$ 360,418	$ 255,439