Investments (Maturity Information) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Investment securities available for sale
Total investment securities available for sale, cost	$ 6,885,797	$ 7,163,574
Investment securities available for sale	6,861,293	7,171,917
Investment securities held to maturity
Investment securities held to maturity	255	518
Debt Securities
Investment securities available for sale
Maturing in one year or less, cost	1,255,714	447,866
Maturing in one through five years, cost	919,086	3,087,521
Maturing in five through ten years, cost	8,500	0
Maturing in over ten years, cost	2,115	0
Maturing in one year or less, fair value	1,255,094	447,992
Maturing in one through five years, fair value	918,448	3,090,621
Maturing in five through ten years, fair value	8,500	0
Maturing in over ten years, fair value	2,160	0
Equity Securities
Investment securities available for sale
Total investment securities available for sale, cost	7,935	0
Investment securities available for sale	8,893	0
Mortgage Backed Securities, Other
Investment securities available for sale
Total investment securities available for sale, cost	4,692,447	3,628,187
Investment securities available for sale	4,668,198	3,633,304
Investment securities held to maturity
Investment securities held to maturity	255	518
Fair Value	$ 265	$ 544

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

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