Investment Securities - Amortized Cost and Fair Value of Available for Sale Securities and Held to Maturity Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Available for Sale, Amortized Cost
Due in one year or less	$ 2,703
Due after one through five years	16,359
Due after five through ten years	60,614
Due after ten years	281,234
Amortized Cost	360,910
Total Investment Securities	696,189
Available for Sale, Fair Value
Due in one year or less	2,717
Due after one through five years	17,068
Due after five through ten years	62,241
Due after ten years	281,763
Fair Value	363,789
Total Investment Securities	696,862
Held to Maturity, Amortized Cost
Due in one year or less	2,046
Due after one through five years	61,921
Due after five through ten years	61,606
Due after ten years	121,857
Amortized Cost	247,430
Amortized Cost	607,643	$ 618,599
Held to Maturity, Fair Value
Due in one year or less	2,047
Due after one through five years	63,193
Due after five through ten years	61,145
Due after ten years	121,906
Fair Value	248,291
Total Investment Securities	611,933	632,380
U.S. Government-sponsored mortgage-backed securities
Available for Sale, Amortized Cost
Without single maturity date	313,459
Available for Sale, Fair Value
Without single maturity date	312,292
Held to Maturity, Amortized Cost
Without single maturity date	360,213
Amortized Cost	360,213	398,832
Held to Maturity, Fair Value
Without single maturity date	363,642
Total Investment Securities	363,642	$ 405,646
Equity securities
Available for Sale, Amortized Cost
Without single maturity date	21,820
Available for Sale, Fair Value
Without single maturity date	$ 20,781