Parent Company Only Financial Information, Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
ASSETS
Cash and due from banks	$ 374,921	$ 444,113
Investment securities available for sale, at fair value	4,967,414	5,396,812
Other assets	1,047,017	1,010,253
Total assets	27,715,021	26,821,774
LIABILITIES AND STOCKHOLDERS’ EQUITY
Commercial paper	67,978	74,297
Senior notes, at par	680,000	680,000
Subordinated notes, at par	250,000	250,000
Other Long-term Debt and Capitalized Costs	(875)	(143)
Total long-term funding	2,679,350	3,930,117
Accrued expenses and other liabilities	222,914	222,285
Total liabilities	24,777,775	24,021,523
Preferred equity	121,379	59,727
Common stock	1,642	1,665
Total stockholders’ equity	2,937,246	2,800,251	$ 2,891,290	$ 2,936,399
Total liabilities and stockholders’ equity	27,715,021	26,821,774
Parent Company [Member]
ASSETS
Cash and due from banks	610,862	523,103
Investment securities available for sale, at fair value	61,847	76,159
Investment in subsidiaries	3,211,685	3,166,080
Other assets	73,781	94,332
Total assets	3,958,175	3,859,674
LIABILITIES AND STOCKHOLDERS’ EQUITY
Commercial paper	67,978	74,297
Senior notes, at par	680,000	680,000
Subordinated notes, at par	250,000	250,000
Other Long-term Debt and Capitalized Costs	(875)	(143)
Total long-term funding	929,125	929,857
Accrued expenses and other liabilities	23,826	55,269
Total liabilities	1,020,929	1,059,423
Preferred equity	121,379	59,727
Common stock	2,815,867	2,740,524
Total stockholders’ equity	2,937,246	2,800,251
Total liabilities and stockholders’ equity	$ 3,958,175	$ 3,859,674