Investment Securities (Investments Classified by Contractual Maturity Date) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Available-for-sale Securities [Abstract]
Available-for-sale, amortized cost, due in one year or less	$ 3,485
Available-for-sale, amortized cost, due after one year through five years	75,171
Available-for-sale, amortized cost, due after five years through ten years	39,777
Available-for-sale, amortized cost, due after ten years	350,317
Available-for-sale, amortized cost, mutual fund	540
Available-for-sale, amortized cost, tax credit investments	0
Available-for-sale securities, debt maturities, amortized cost basis	469,290
Available-for-sale, estimated fair value, due in one year or less	3,495
Available-for-sale, estimated fair value, due after one year through five years	75,533
Available-for-sale, estimated fair value, due after five years through ten years	39,912
Available-for-sale, estimated fair value, due after ten years	350,223
Available-for-sale, estimated fair value, mutual fund	557
Available-for-sale, estimated fair value, tax credit investments	0
Available-for-sale securities, debt securities	469,720
Held-to-maturity Securities
Held-to-maturity securities, amortized cost, due in one year or less	1,834
Held-to-maturity securities, amortized cost, due after one year through five years	37,830
Held-to-maturity securities, amortized cost, due after five years through ten years	82,476
Held-to-maturity securities, amortized cost, due after ten years	16,769
Held-to-maturity securities, amortized cost, mutual fund	0
Held-to-maturity securities, amortized cost, tax credit investments	287
Held-to-maturity securities, debt maturities, net carrying amount	139,196	$ 140,557
Held-to-maturity, estimated fair value, due in one year or less	1,836
Held-to-maturity, estimated fair value, due after one year through five years	38,134
Held-to-maturity, estimated fair value, due after five years through ten years	84,533
Held-to-maturity, estimated fair value, due after ten years	16,804
Held-to-maturity, estimated fair value, mutual fund	0
Held-to-maturity, estimated fair value, tax credit investments	287
Held-to-maturity securities, estimated fair value	$ 141,594	$ 142,272