Parent Company Only Financials Balance Sheet (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
ASSETS
Cash and due from banks	$ 455,482	$ 563,304
Investment securities available for sale, at fair value	5,250,585	4,926,758
Other assets	1,006,697	926,417
Total assets	24,226,920	23,487,735
LIABILITIES AND STOCKHOLDERS' EQUITY
Commercial paper	65,484	51,484
Senior notes, at par	585,000	585,000
Subordinated debt, at par	0	25,821
Total long-term funding	3,087,267	1,015,346
Accrued expenses and other liabilities	193,800	192,843
Total liabilities	21,335,630	20,551,336
Preferred equity	61,862	63,272
Common stock	1,750	1,750
Total Stockholders' equity	2,891,290	2,936,399	2,865,794	3,158,791
Total liabilities and stockholders' equity	24,226,920	23,487,735
Parent Company [Member]
ASSETS
Cash and due from banks	148,327	159,725
Investment securities available for sale, at fair value	163,679	200,800
Notes receivable from subsidiaries	46,594	47,455
Investment in subsidiaries	3,161,153	3,250,667
Other assets	81,529	74,507
Total assets	3,601,282	3,733,154
LIABILITIES AND STOCKHOLDERS' EQUITY
Commercial paper	65,484	51,245
Senior notes, at par	585,000	585,000
Subordinated debt, at par	0	25,821
Long-term funding capitalized costs	1,941	2,590
Total long-term funding	586,941	613,411
Accrued expenses and other liabilities	57,567	132,099
Total liabilities	709,992	796,755
Preferred equity	61,862	63,272
Common stock	2,829,428	2,873,127
Total Stockholders' equity	2,891,290	2,936,399
Total liabilities and stockholders' equity	$ 3,601,282	$ 3,733,154