Parent Company Only Financial Statements Parent Company Only Financial Statements, Condensed Cash Flow Statement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flows From Operating Activities: [Abstract]
Net income	$ 446,424	$ 335,685	$ 232,281
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Change in other assets	27,507	(5,506)	(49,565)
Change in other liabilities	(139,346)	182,184	(11,413)
Net cash provided by operating activities	(552,006)	214,931	(91,949)
Cash Flows From Investing Activities: [Abstract]
Proceeds from sales of available for sale securities	745,643	1,309,215	899,381
Acquisitions, net of cash acquired	(175,755)	0	56,017
Net cash used in investing activities	(1,807,631)	739,556	(286,007)
Cash Flows From Financing Activities: [Abstract]
Net change in other borrowed funds	1,295,484	(10,909)	(606,476)
Issuance of subordinated debentures, net of issuance costs	0	0	144,615
Issuance of common and treasury stock, net	(88)	4,368	12,455
Dividends paid	(127,188)	(116,041)	(113,455)
Repurchase of common stock	(53,465)	(7,403)	(66,792)
Net cash used in financing activities	1,186,007	(1,174,930)	271,854
Net increase (decrease) in cash and cash equivalents	(1,173,630)	(220,443)	(106,102)
Cash and cash equivalents at beginning of period	2,317,054	2,537,497	2,643,599
Cash and cash equivalents at end of period	1,143,424	2,317,054	2,537,497
Cash paid for interest	243,121	127,513	82,876
Parent Company [Member]
Cash Flows From Operating Activities: [Abstract]
Net income	445,646	334,644	232,668
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Equity in undistributed income of bank subsidiaries	(37,515)	(181,552)	(216,120)
Equity in undistributed income of non-bank subsidiaries	(12,914)	(9,545)	(21,984)
Change in other assets	1,072	(12)	2,933
Change in other liabilities	(13,434)	7,457	(1,285)
Net cash provided by operating activities	406,539	170,106	34,314
Cash Flows From Investing Activities: [Abstract]
Proceeds from sales of available for sale securities	0	3,000	1,632
Investment in subsidiaries	(31,901)	(4,355)	(26,000)
Acquisitions, net of cash acquired	(232,680)	0	(105,520)
Net cash used in investing activities	(264,581)	(1,355)	(129,888)
Cash Flows From Financing Activities: [Abstract]
Net change in other borrowed funds	0	(7,217)	0
Issuance of subordinated debentures, net of issuance costs	0	0	144,615
Issuance of common and treasury stock, net	(88)	4,368	12,455
Dividends paid	127,188	116,041	113,455
Repurchase of common stock	53,465	7,403	66,792
Net cash used in financing activities	(180,741)	(126,293)	(23,177)
Net increase (decrease) in cash and cash equivalents	(38,783)	42,458	(118,751)
Cash and cash equivalents at beginning of period	205,876	163,418	282,169
Cash and cash equivalents at end of period	167,093	205,876	163,418
Cash paid for interest	$ 11,457	$ 6,211	$ 4,127