Securities (Schedule of Contractual Maturities of Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Available for Sale, Amortized Cost
Available for sale Securities, Amortized Cost	$ 426,340	$ 363,366
Available for Sale, Fair Value
Available for sale Securities, Fair Value, Total	429,125	363,644
Held to Maturity, Amortized Cost
Held to maturity Securities, Amortized Cost	478,798	487,076
Held to Maturity, Fair Value
Held to Maturity, Fair Value, Total	479,662	$ 485,650
Debt Securities
Available for Sale, Amortized Cost
Available for Sale, Amortized Cost, Due in one year or less	3,229
Available for Sale, Amortized Cost, Due after one year to five years	36,704
Available for Sale, Amortized Cost, Due after five to ten years	105,842
Available for Sale, Amortized Cost, Due after ten years	261,389
Available for sale Securities, Amortized Cost	407,164
Available for Sale, Fair Value
Available for Sale, Fair Value, Due in one year or less	3,237
Available for Sale, Fair Value, Due after one year to five years	37,152
Available for Sale, Fair Value, Due after five to ten years	106,576
Available for Sale, Fair Value, Due after ten years	262,049
Available for sale Securities, Fair Value, Total	409,014
Held to Maturity, Amortized Cost
Held to Maturity, Amortized Cost, Due in one year or less	0
Held to Maturity, Amortized Cost, Due after one year to five years	15,731
Held to Maturity, Amortized Cost, Due after five to ten years	18,158
Held to Maturity, Amortized Cost, Due after ten years	444,909
Held to maturity Securities, Amortized Cost	478,798
Held to Maturity, Fair Value
Held to Maturity, Fair Value, Due in one year or less	0
Held to Maturity, Fair Value, Due after one year to five years	15,917
Held to Maturity, Fair Value, Due after five to ten years	18,654
Held to Maturity, Fair Value, Due after ten years	445,091
Held to Maturity, Fair Value, Total	479,662
Equity securities
Available for Sale, Amortized Cost
Available for Sale, Amortized Cost, Marketable equity securities	19,176
Available for Sale, Fair Value
Available for Sale, Fair Value, Marketable equity securities	20,111
Held to Maturity, Amortized Cost
Held to maturity Securities, Amortized Cost	0
Held to Maturity, Fair Value
Held to Maturity, Fair Value, Total	$ 0