Investments (Maturity Information) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Investment securities available for sale
Total investment securities available for sale, cost	$ 5,404,335	$ 5,192,419
Investment securities available for sale	5,387,703	5,226,228
Investment securities held to maturity
Investment securities held to maturity	907	1,342
Debt Securities
Investment securities available for sale
Maturing in one year or less, cost	839,956	2,285,159
Maturing in one through five years, cost	2,077,539	1,590,608
Maturing in five through ten years, cost	0	898
Maturing in one year or less, fair value	840,883	2,286,403
Maturing in one through five years, fair value	2,077,800	1,592,923
Maturing in five through ten years, fair value	0	880
Equity Securities
Investment securities available for sale
Total investment securities available for sale, cost	543	543
Investment securities available for sale	22,147	16,365
Mortgage Backed Securities, Other [Member]
Investment securities available for sale
Total investment securities available for sale, cost	2,486,297	1,315,211
Investment securities available for sale	2,446,873	1,329,657
Investment securities held to maturity
Investment securities held to maturity	907	1,342
Fair Value	$ 974	$ 1,448