Investment Securities - Amortized Cost and Fair Value of Available for Sale Securities and Held to Maturity Securities by Contractual Maturity (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013
Available for Sale
Due in one year or less - Amortized Cost	$ 6,554
Due after one through five years - Amortized Cost	13,272
Due after five through ten years - Amortized Cost	56,466
Due after ten years - Amortized Cost	118,909
Total debt securities with a single maturity date - Amortized Cost	195,201
Total Investment Securities - Amortized Cost	587,021
Due in one year or less - Fair Value	6,735
Due after one through five years - Fair Value	13,763
Due after five through ten years - Fair Value	57,995
Due after ten years - Fair Value	113,411
Total debt securities with a single maturity date - Fair Value	191,904
Total Investment Securities - Fair Value	584,593
Held to Maturity
Due in one year or less - Amortized Cost	1,755
Due after one through five years - Amortized Cost	9,429
Due after five through ten years - Amortized Cost	58,321
Due after ten years - Amortized Cost	46,438
Total debt securities with a single maturity date - Amortized Cost	115,943
Total Investment Securities - Amortized Cost	324,399
Due in one year or less - Fair Value	1,757
Due after one through five years - Fair Value	9,692
Due after five through ten years - Fair Value	58,326
Due after ten years - Fair Value	46,709
Total debt securities with a single maturity date - Fair Value	116,484
Total Investment Securities - Fair Value	331,765
U.S. Government-sponsored mortgage-backed securities
Available for Sale
Without single maturity date - Amortized Cost	390,114
Without single maturity date - Fair Value	390,983
Held to Maturity
Without single maturity date - Amortized Cost	208,456
Without single maturity date - Fair Value	215,281
Equity securities
Available for Sale
Without single maturity date - Amortized Cost	1,706
Without single maturity date - Fair Value	$ 1,706