Securities Available for Sale - Amortized Cost and Estimated Fair Value (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Amortized Cost - Due within one year	$ 0
Amortized Cost - Due after one year through five years	340,000
Amortized Cost - Due after five years through ten years	3,884,000
Amortized Cost - Due after ten years	5,975,000
Amortized Cost	746,537,000	723,401,000
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Estimated Fair Value - Due within one year	0
Estimated Fair Value - Due after one year through five years	348,000
Estimated Fair Value - Due after five years through ten years	4,292,000
Estimated Fair Value - Due after ten years	5,442,000
Estimated Fair Value	746,683,000	705,751,000
Available-for-sale Securities, Restricted	356,800,000	360,600,000
GSE collateralized mortgage obligations
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Amortized Cost - no single maturity date	291,676,000
Amortized Cost	291,676,000	286,608,000
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Estimated Fair Value - no single maturity date	288,138,000
Estimated Fair Value	288,138,000	274,101,000
GSE mortgage-backed securities
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Amortized Cost - no single maturity date	427,237,000
Amortized Cost	427,237,000	409,165,000
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Estimated Fair Value - no single maturity date	431,194,000
Estimated Fair Value	431,194,000	404,996,000
Mutual funds - GSE mortgage related securities
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Amortized Cost - no single maturity date	17,425,000
Amortized Cost	17,425,000	17,425,000
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Estimated Fair Value - no single maturity date	17,269,000
Estimated Fair Value	$ 17,269,000	$ 17,021,000