Investments (Maturity Information) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Investment securities available for sale
Total investment securities available for sale, cost	$ 5,632,720	$ 5,404,335
Total investment securities available for sale, fair value	5,648,094	5,387,703
Investment securities held to maturity
Investment securities held to maturity	607	907
Debt Securities
Investment securities available for sale
Maturing in one year or less, cost	529,931	839,956
Maturing in one through five years, cost	2,487,593	2,077,539
Maturing in over ten years, cost	23,012	0
Maturing in one year or less, fair value	530,363	840,883
Maturing in one through five years, fair value	2,487,226	2,077,800
Maturing in over ten years, fair value	23,012	0
Equity Securities
Investment securities available for sale
Total investment securities available for sale, cost	543	543
Total investment securities available for sale, fair value	30,028	22,147
Mortgage Backed Securities, Other [Member]
Investment securities available for sale
Total investment securities available for sale, cost	2,591,641	2,486,297
Total investment securities available for sale, fair value	2,577,465	2,446,873
Investment securities held to maturity
Investment securities held to maturity	607	907
Fair Value	$ 638	$ 974

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount after adjustments of available-for-sale debt securities at cost, maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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