Parent Company Only Financial Statements Parent Company Only Financial Statements, Condensed Cash Flow Statement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Flows From Operating Activities: [Abstract]
Net income	$ 500,685	$ 446,424	$ 335,685
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Change in other assets	18,955	27,507	(5,506)
Change in other liabilities	57,569	(139,346)	182,184
Net cash provided by operating activities	(473,679)	(552,006)	214,931
Cash Flows From Investing Activities: [Abstract]
Proceeds from sales of available for sale securities	1,211,718	745,643	1,309,215
Acquisitions, net of cash acquired	0	(175,755)	0
Net cash used in investing activities	(2,323,737)	(1,807,631)	739,556
Cash Flows From Financing Activities: [Abstract]
Net change in other borrowed funds	1,110,970	1,295,484	(10,909)
Issuance of common and treasury stock, net	(7)	(88)	4,368
Dividends paid	(143,496)	(127,188)	(116,041)
Repurchase of common stock	(129,483)	(53,465)	(7,403)
Net cash used in financing activities	2,912,813	1,186,007	(1,174,930)
Net increase (decrease) in cash and cash equivalents	115,397	(1,173,630)	(220,443)
Cash and cash equivalents at beginning of period	1,143,424	2,317,054	2,537,497
Cash and cash equivalents at end of period	1,258,821	1,143,424	2,317,054
Cash paid for interest	417,070	243,121	127,513
Parent Company [Member]
Cash Flows From Operating Activities: [Abstract]
Net income	500,758	445,646	334,644
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Equity in undistributed income of bank subsidiaries	(166,797)	(37,515)	(181,552)
Equity in undistributed income of non-bank subsidiaries	(10,768)	(12,914)	(9,545)
Change in other assets	5,075	1,072	(12)
Change in other liabilities	855	(13,434)	7,457
Net cash provided by operating activities	340,509	406,539	170,106
Cash Flows From Investing Activities: [Abstract]
Proceeds from sales of available for sale securities	0	0	3,000
Investment in subsidiaries	(19,837)	(31,901)	(4,355)
Acquisitions, net of cash acquired	0	(232,680)	0
Net cash used in investing activities	(19,837)	(264,581)	(1,355)
Cash Flows From Financing Activities: [Abstract]
Net change in other borrowed funds	0	0	(7,217)
Issuance of common and treasury stock, net	(7)	(88)	4,368
Dividends paid	143,496	127,188	116,041
Repurchase of common stock	129,483	53,465	7,403
Net cash used in financing activities	(272,986)	(180,741)	(126,293)
Net increase (decrease) in cash and cash equivalents	47,686	(38,783)	42,458
Cash and cash equivalents at beginning of period	167,093	205,876	163,418
Cash and cash equivalents at end of period	214,779	167,093	205,876
Cash paid for interest	$ 15,099	$ 11,457	$ 6,211