Investments (Maturity Information) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Investment securities available for sale
Total investment securities available for sale, cost	$ 6,663,652	$ 7,163,574
Total investment securities available for sale, fair value	6,690,578	7,171,917
Investment securities held to maturity
Investment securities held to maturity	301	518
Debt Securities
Investment securities available for sale
Maturing in one year or less, cost	673,879	447,866
Maturing in one through five years, cost	1,645,077	3,087,521
Maturing in one year or less, fair value	675,164	447,992
Maturing in one through five years, fair value	1,651,242	3,090,621
Equity Securities
Investment securities available for sale
Total investment securities available for sale, cost	1,591	0
Total investment securities available for sale, fair value	$ 1,611	$ 0

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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Fair value of available-for-sale debt securities maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount after adjustments of available-for-sale debt securities at cost, maturing in the next 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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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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