Investment Securities Schedule of Amortized Cost and Fair Values of Debt Securities by Contractual Maturities (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014
Statement of Investments [Line Items]
Available-for-sale Securities, Debt Maturities, within One Year, Amortized Cost Basis	$ 20,164
Available-for-sale Securities, Debt Maturities, within One Year, Fair Value	20,226
Available-for-sale Securities, Debt Maturities, after One Through Five Years, Amortized Cost Basis	71,674
Available-for-sale Securities, Debt Maturities, after One Through Five Years, Fair Value	75,583
Available-for-sale Securities, Debt Maturities, after Five Through Ten Years, Amortized Cost Basis	194,644
Available-for-sale Securities, Debt Maturities, after Five Through Ten Years, Fair Value	200,454
Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis	234,762
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	221,929
Available for Sale Securities, Debt Securities, Amortized Cost, Before Securities Without Debt Maturities	521,244
Available for Sale Securities, Debt Maturities, Before Securities Without Single Maturities	518,192
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis	2,462,182
Available for Sale, Estimated Fair Value	2,451,528
Collateralized Mortgage Backed Securities [Member]
Statement of Investments [Line Items]
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis	1,022,728
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value	1,002,731
Collateralized Mortgage Obligations [Member]
Statement of Investments [Line Items]
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis	918,210
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value	$ 930,605