Securities (Securities by Contractual Maturity) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale debt securities maturities wIthin 1 year amortized cost	$ 62,120
Available for sale debt securities maturities 1-5 years amortized cost	247,054
Available for sale debt securities maturities 5-10 years amortized cost	285,543
Available for sale debt securities maturities after 10 years amortized cost	196,084
Available for sale securities amortized cost	790,801
Available for sale debt securities maturities within 1 year fair value	61,700
Available for sale debt securities maturities 1-5 years fair value	244,392
Available for sale debt securities maturities 5-10 years fair value	280,870
Available for sale debt securities maturities after 10 years fair value	193,992
Available for sale debt securities fair value	780,954
Held to maturity debt securities maturities within 1 year amortized cost	1,719
Held to maturity debt securities maturities 1-5 years amortized cost	5,374
Held to maturity debt securities maturities 5-10 years amortized cost	4,019
Held to maturity debt securities maturities after 10 years amortized cost	1,429
Held to maturity securities amortized cost	12,541	$ 15,633
Held to maturity debt securities maturities within 1 year fair value	1,743
Held to maturity debt securities maturities 1-5 years fair value	5,451
Held to maturity debt securities maturities 5-10 years fair value	4,077
Held to maturity debt securities maturities after 10 years fair value	1,450
Held to maturity securities fair value	12,721	15,920
Mortgage-backed securities issued by U.S. government-sponsored agencies and U.S. government-sponsored enterprises [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Held to maturity securities amortized cost	12,541	15,633
Held to maturity securities fair value	$ 12,721	$ 15,920