Investments Maturities of AFS Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis	$ 78,573
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis	339,665
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Amortized Cost Basis	199,337
Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis	518,305
Investment securities available for sale at amortized cost	1,135,880	$ 1,084,105
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	78,999
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value	345,000
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value	203,373
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	524,157
Available-for-sale Securities	$ 1,151,529	$ 1,084,510