Parent Company Information (Components of Condensed Income Statement The Parent Company) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Income:
Other non-interest income	$ 76,763	$ 75,060	$ 60,076	$ 73,378	$ 70,919	$ 69,931	$ 75,853	$ 68,612
Total operating income									$ 417,724	$ 524,492	$ 483,633
Operating Expense:
Compensation and benefits									428,391	395,402	381,496
Non-interest expense									78,228	98,617	91,046
Income tax benefit	(15,118)	(18,289)	(14,802)	(11,144)	(25,966)	(25,411)	(26,451)	(26,141)	(59,353)	(103,969)	(81,215)
Net income	$ 60,044	$ 69,281	$ 53,097	$ 38,199	$ 90,473	$ 93,865	$ 98,649	$ 99,736	220,621	382,723	360,418
Parent Company [Member]
Operating Income:
Dividend income from bank subsidiary									20,000	360,000	290,000
Interest on securities and deposits									5,530	10,728	7,342
Alternative investments income									2,467	(256)	290
Other non-interest income									634	382	805
Total operating income									28,631	370,854	298,437
Operating Expense:
Interest expense on borrowings									18,684	21,062	11,127
Non-interest expense									16,426	15,527	19,105
Total operating expense									35,110	36,589	30,232
Income before income tax benefit and equity in undistributed earnings of subsidiaries									(6,479)	334,265	268,205
Income tax benefit									4,572	4,671	2,207
Equity in undistributed earnings of subsidiaries									222,528	43,787	90,006
Net income									$ 220,621	$ 382,723	$ 360,418