Parent Company Information (Components of Condensed Cash Flow The Parent Company) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net cash provided by operating activities	$ 303,850	$ 469,408	$ 444,966
Investing activities:
Alternative investments capital call	(6,065)	(1,215)	873
Proceeds from redemption of other assets	0	0	7,581
Net cash provided by (used for) investing activities	(2,549,756)	(1,317,924)	(531,053)
Financing activities:
Issuance of Series F preferred stock	0	0	145,056
Redemption of Series E preferred stock	0	0	(122,710)
Cash dividends paid to common shareholders	(140,783)	(114,959)	(94,630)
Cash dividends paid to preferred shareholders	(7,875)	(7,875)	(8,096)
Exercise of stock options	619	2,173	8,259
Common stock repurchased and acquired from stock compensation plan activity	(13,003)	(12,158)	(11,585)
Net cash (used for) provided by financing activities	2,174,302	921,229	122,749
Net (decrease) increase in cash and cash equivalents	(71,604)	72,713	36,662
Cash and due from banks at beginning of year	329,499	256,786	220,124
Cash and due from banks at end of year	257,895	329,499	256,786
Parent Company [Member]
Operating activities:
Net cash provided by operating activities	362,617	282,986	115,957
Investing activities:
Alternative investments capital call	(1,850)	0	0
Investment in subsidiaries	(296,000)	0	0
Proceeds from redemption of other assets	0	0	7,581
Net cash provided by (used for) investing activities	(297,850)	0	7,581
Financing activities:
Issuance of long-term debt	296,358	0	0
Issuance of Series F preferred stock	0	0	145,056
Redemption of Series E preferred stock	0	0	122,710
Cash dividends paid to common shareholders	140,783	114,959	94,630
Cash dividends paid to preferred shareholders	7,875	7,875	8,096
Exercise of stock options	619	2,173	8,259
Common stock repurchased and acquired from stock compensation plan activity	19,619	25,937	23,279
Net cash (used for) provided by financing activities	128,700	(146,598)	(95,400)
Net (decrease) increase in cash and cash equivalents	193,467	136,388	28,138
Cash and due from banks at beginning of year	317,473	181,085	152,947
Cash and due from banks at end of year	$ 510,940	$ 317,473	$ 181,085