Investment Securities - Amortized Cost and Fair Value of Available for Sale Securities and Held to Maturity Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Amortized Cost
Due in one year or less	$ 3,065	$ 4,658
Due after one through five years	19,909	13,725
Due after five through ten years	60,972	52,878
Due after ten years	245,227	220,600
Total debt securities with a single maturity date	329,173	291,861
Total Investment Securities	625,877	640,499
Fair Value
Due in one year or less	3,086	4,704
Due after one through five years	21,060	14,295
Due after five through ten years	64,871	55,375
Due after ten years	264,596	231,672
Total debt securities with a single maturity date	353,613	306,046
Total Investment Securities	658,829	658,400
Amortized Cost
Due in one year or less	2,500	4,144
Due after one through five years	42,528	28,054
Due after five through ten years	82,937	81,483
Due after ten years	108,746	106,086
Total debt securities with a single maturity date	236,711	219,767
Total Investment Securities	638,972	618,599
Fair Value
Due in one year or less	2,532	4,148
Due after one through five years	44,205	29,175
Due after five through ten years	85,365	83,646
Due after ten years	116,259	109,765
Total debt securities with a single maturity date	248,361	226,734
Investment securities held to maturity	665,066	632,380
U.S. Government-sponsored mortgage-backed securities
Amortized Cost
Without single maturity date	292,822	342,550
Fair Value
Without single maturity date	301,271	346,266
Amortized Cost
Without single maturity date	402,261	398,832
Total Investment Securities	402,261	398,832
Fair Value
Without single maturity date	416,705	405,646
Investment securities held to maturity	416,705	405,646
Equity securities
Amortized Cost
Without single maturity date	3,882	3,912
Fair Value
Without single maturity date	3,945	3,912
Amortized Cost
Without single maturity date
Fair Value
Without single maturity date
Certificates of deposit
Amortized Cost
Without single maturity date		2,176
Fair Value
Without single maturity date		2,176
Amortized Cost
Without single maturity date
Fair Value
Without single maturity date