Investment Securities Schedule of Amortized Cost and Fair Values of Debt Securities by Contractual Maturities (Details) $ in Thousands	Jun. 30, 2015 USD ($)
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Maturities, within One Year, Amortized Cost Basis	$ 57,382
Available-for-sale Securities, Debt Maturities, within One Year, Fair Value	58,372
Available-for-sale Securities, Debt Maturities, after One Through Five Years, Amortized Cost Basis	104,022
Available-for-sale Securities, Debt Maturities, after One Through Five Years, Fair Value	106,663
Available-for-sale Securities, Debt Maturities, after Five Through Ten Years, Amortized Cost Basis	148,682
Available-for-sale Securities, Debt Maturities, after Five Through Ten Years, Fair Value	151,430
Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis	175,099
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	164,090
Available for Sale Securities, Debt Securities, Amortized Cost, Before Securities Without Debt Maturities	485,185
Available for Sale Securities, Debt Maturities, Before Securities Without Single Maturities	480,555
Available-for-sale Debt Securities, Amortized Cost Basis	2,414,696
Available for Sale, Estimated Fair Value	2,407,451
Collateralized Mortgage Obligations [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis	931,093
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value	918,232
Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis	998,418
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value	$ 1,008,664