Parent Company Financial Information (Condensed Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Held-to-maturity, fair value	$ 850,473	$ 552,088
Cash and due from banks	737,327	798,319	$ 841,942	$ 1,173,057
Interest-bearing deposits	1,410,852	6,108,124
Held-to-maturity Securities	867,904	545,648
Available-for-sale, at fair value	13,372,194	7,643,116
Other noninterest-bearing investments	884,407	848,144
Other assets	983,355	916,937
Total assets	63,239,165	59,664,543
Other liabilities	941,999	548,742
Long-term debt	534,850	812,366
Total liabilities	55,604,859	52,157,024
Preferred stock	709,601	828,490
Common Stock	4,724,715	4,766,731
Retained earnings	2,321,571	1,966,910
Accumulated Other Comprehensive Income (Loss), Net of Tax	(121,581)	(54,612)	(128,041)
Total shareholders' equity	7,634,306	7,507,519	7,369,530	6,464,563
Total liabilities and shareholders' equity	63,239,165	59,664,543
Allowance for loan losses	567,522	606,048	604,663
Parent Company [Member]
Cash and due from banks	2,023	18,375	$ 23,774	$ 903,078
Interest-bearing deposits	528,531	775,649
Security Resell Agreements Amount Outstanding	0	100,000
Available-for-sale, at fair value	40,258	45,168
Other noninterest-bearing investments	28,719	28,178
Receivables From Subsidiaries, Others	0	60
Other assets	80,715	78,728
Total assets	8,256,893	8,442,822
Other liabilities	88,477	123,849
Subordinated debt to affiliated trusts	0	164,950
Total liabilities	622,587	935,303
Preferred stock	709,601	828,490
Common Stock	4,724,715	4,766,731
Retained earnings	2,321,571	1,966,910
Accumulated Other Comprehensive Income (Loss), Net of Tax	(121,581)	(54,612)
Total shareholders' equity	7,634,306	7,507,519
Total liabilities and shareholders' equity	8,256,893	8,442,822
Parent Company [Member] | Due To Others [Member]
Long-term debt	534,110	646,504
Parent Company [Member] | Other Operating Companies [Member]
Investments in subsidiaries	6,126	84,010
Parent Company [Member] | Commercial Banks And Bank Holding Company [Member]
Investments in subsidiaries	$ 7,570,521	$ 7,312,654