Investment Securities (Investments Classified by Contractual Maturity Date) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Available-for-sale Securities [Abstract]
Available-for-sale, amortized cost, due in one year or less	$ 10,397
Available-for-sale, amortized cost, due after one year through five years	68,008
Available-for-sale, amortized cost, due after five years through ten years	40,715
Available-for-sale, amortized cost, due after ten years	398,821
Available-for-sale, amortized cost, mutual fund	534
Available-for-sale, amortized cost, tax credit investments	0
Available-for-sale securities, debt maturities, amortized cost basis	518,475
Available-for-sale, estimated fair value, due in one year or less	10,427
Available-for-sale, estimated fair value, due after one year through five years	68,389
Available-for-sale, estimated fair value, due after five years through ten years	41,060
Available-for-sale, estimated fair value, due after ten years	402,848
Available-for-sale, estimated fair value, mutual fund	551
Available-for-sale, estimated fair value, tax credit investments	0
Available-for-sale securities, debt securities	523,275
Held-to-maturity Securities
Held-to-maturity securities, amortized cost, due in one year or less	0
Held-to-maturity securities, amortized cost, due after one year through five years	30,431
Held-to-maturity securities, amortized cost, due after five years through ten years	90,472
Held-to-maturity securities, amortized cost, due after ten years	20,133
Held-to-maturity securities, amortized cost, mutual fund	0
Held-to-maturity securities, amortized cost, tax credit investments	290
Held-to-maturity securities, debt maturities, net carrying amount	141,326	$ 139,424
Held-to-maturity, estimated fair value, due in one year or less	0
Held-to-maturity, estimated fair value, due after one year through five years	31,165
Held-to-maturity, estimated fair value, due after five years through ten years	95,870
Held-to-maturity, estimated fair value, due after ten years	20,888
Held-to-maturity, estimated fair value, mutual fund	0
Held-to-maturity, estimated fair value, tax credit investments	290
Held-to-maturity securities, estimated fair value	$ 148,213	$ 142,260