Securities (Securities by Contractual Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available for Sale and Held to Maturty Securities [Line Items]
Available for sale debt securities maturities within 1 year amortized cost	$ 64,023
Available for sale debt securities maturities 1-5 years amortized cost	314,353
Available for sale debt securities maturities 5-10 years amortized cost	278,106
Available for sale debt securities maturities after 10 years amortized cost	189,617
Available for sale debt securities maturities total amortized cost	846,099
Available for sale debt securities maturities within 1 year fair value	61,577
Available for sale debt securities maturities 1-5 years fair value	302,124
Available for sale debt securities maturities 5-10 years fair value	266,878
Available for sale debt securities maturities after 10 years fair value	182,068
Available for sale debt securities fair value	812,647
Held to maturity debt securities maturities within 1 year amortized cost	1,370
Held to maturity debt securities maturities 1-5 years amortized cost	4,529
Held to maturity debt securities maturities 5-10 years amortized cost	3,709
Held to maturity debt securities maturities after 10 years amortized cost	1,255
Held to maturity securities	10,863	$ 12,541
Held to maturity debt securities maturities within 1 year fair value	1,344
Held to maturity debt securities maturities 1-5 years fair value	4,443
Held to maturity debt securities maturities 5-10 years fair value	3,639
Held to maturity debt securities maturities after 10 years fair value	1,231
Held to maturity securities fair value	$ 10,657	$ 12,721