Investments Maturities of AFS Securities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis	$ 59,431
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	59,895
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis	279,380
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value	281,892
Investment securities available for sale at amortized cost	728,989	690,556
Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis	308,537
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	312,109
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Amortized Cost Basis	81,641
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value	82,714
Available-for-sale Securities	$ 736,610	$ 699,300

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

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