Parent Company Only Financial Statements Parent Company Only Financial Statements, Condensed Balance Sheet Statement (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets [Abstract]
Cash and cash equivalents	$ 1,258,821	$ 1,143,424	$ 2,317,054	$ 2,537,497
Loan to bank subsidiary	21,540,228	21,449,273
Other assets	547,995	446,891
Total assets	42,172,021	38,020,504
Liabilities [Abstract]
Other liabilities	372,230	183,480
Subordinated debentures	275,923	275,913
Total liabilities	37,308,102	33,577,459
Shareholders' equity: [Abstract]
Common stock	5	5
Capital surplus	1,350,995	1,334,030
Retained earnings	3,729,778	3,369,654
Treasury stock	(329,906)	(198,995)
Accumulated other comprehensive income (loss)	104,923	(72,585)	(36,174)	(10,967)
Total shareholders’ equity	4,855,795	4,432,109
Total liabilities and shareholders’ equity	42,172,021	38,020,504
Parent Company [Member]
Assets [Abstract]
Cash and cash equivalents	214,779	167,093	$ 205,876	$ 163,418
Loan to bank subsidiary	65,220	65,228
Investment in bank subsidiaries	4,602,977	4,236,654
Investment in non-bank subsidiaries	216,542	218,007
Other assets	38,082	32,999
Total assets	5,137,600	4,719,981
Liabilities [Abstract]
Other liabilities	5,882	11,959
Subordinated debentures	275,923	275,913
Total liabilities	281,805	287,872
Shareholders' equity: [Abstract]
Common stock	5	5
Capital surplus	1,350,995	1,334,030
Retained earnings	3,729,778	3,369,654
Treasury stock	329,906	198,995
Accumulated other comprehensive income (loss)	104,923	(72,585)
Total shareholders’ equity	4,855,795	4,432,109
Total liabilities and shareholders’ equity	$ 5,137,600	$ 4,719,981