Securities (Securities by Contractual Maturity) (Details) - USD ($) $ in Thousands	Mar. 31, 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	$ 63,132
Available for sale debt securities maturities 1-5 years amortized cost	262,288
Available for sale debt securities maturities 5-10 years amortized cost	290,876
Available for sale debt securities maturities after 10 years amortized cost	195,006
Available for sale debt securities maturities total amortized cost	811,302
Available for sale debt securities maturities within 1 year fair value	61,513
Available for sale debt securities maturities 1-5 years fair value	254,949
Available for sale debt securities maturities 5-10 years fair value	281,962
Available for sale debt securities maturities after 10 years fair value	189,418
Available for sale debt securities fair value	787,842
Held to maturity debt securities maturities within 1 year amortized cost	1,663
Held to maturity debt securities maturities 1-5 years amortized cost	5,192
Held to maturity debt securities maturities 5-10 years amortized cost	3,840
Held to maturity debt securities maturities after 10 years amortized cost	1,278
Held to maturity securities	11,973	$ 12,541
Held to maturity debt securities maturities within 1 year fair value	1,666
Held to maturity debt securities maturities 1-5 years fair value	5,202
Held to maturity debt securities maturities 5-10 years fair value	3,847
Held to maturity debt securities maturities after 10 years fair value	1,280
Held to maturity securities fair value	$ 11,995	$ 12,721