Investments Maturities of AFS Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis	$ 73,320
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis	334,864
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Amortized Cost Basis	304,561
Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis	435,781
Investment securities available for sale at amortized cost	1,148,526	$ 1,182,427
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	73,128
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value	329,235
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value	291,757
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	424,377
Available-for-sale Securities	$ 1,118,497	$ 1,170,328

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

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Fair value of available-for-sale debt securities maturing in the sixth fiscal year through the tenth 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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