Investment Securities AFS Contractual Maturity Table (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Amortized cost and fair values of investment securities available for sale by contractual maturity
Securities available for sale, debt securities due in one year or less, amortized cost	$ 23,534
Securities available for sale, debt securities due after one year through five years, amortized cost	202,811
Securities available for sale, debt securities due after five years through ten years, amortized cost	404,168
Securities available for sale, debt securities due after ten years, amortized cost	15,623
Total available for sale debt securities, amortized cost	646,136
Securities available for sale, debt securities due in one year or less, fair value	23,714
Securities available for sale, debt securities due after one year through five years, fair value	212,978
Securities available for sale, debt securities due after five years through ten years, fair value	418,321
Securities available for sale, debt securities due after ten years, fair value	16,054
Total available for sale debt securities, Fair value	671,067
Investment securities available for sale, amortized cost	5,277,650	5,270,576
Investment securities available for sale, fair value	5,277,908	5,250,585
Ratio of Fair Value to Amortized Cost, AFS	100.00%
Government-Sponsored Enterprise (GSE) [Member]
Amortized cost and fair values of investment securities available for sale by contractual maturity
Investment securities available for sale, amortized cost	3,767,991	3,855,467
Investment securities available for sale, fair value	3,769,242	3,838,430
Private Label [Member]
Amortized cost and fair values of investment securities available for sale by contractual maturity
Investment securities available for sale, amortized cost	2,699	3,035
Investment securities available for sale, fair value	2,697	3,014
GNMA commercial mortgage-related securities [Member]
Amortized cost and fair values of investment securities available for sale by contractual maturity
Investment securities available for sale, amortized cost	839,488	673,555
Investment securities available for sale, fair value	813,567	647,477
Asset-backed Securities [Member]
Amortized cost and fair values of investment securities available for sale by contractual maturity
Investment securities available for sale, amortized cost	21,318	23,049
Investment securities available for sale, fair value	21,282	23,059
Equity Securities [Member]
Amortized cost and fair values of investment securities available for sale by contractual maturity
Investment securities available for sale, amortized cost	18
Investment securities available for sale, fair value	$ 53

Ratio of Fair Value to Amortized Cost, AFS

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

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Amount of available-for-sale debt securities at cost, net of adjustments, maturing in the sixth fiscal year through the tenth 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 any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

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