Securities (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) security	Dec. 31, 2016 USD ($) security
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Securities available for sale and held to maturity pledged as collateral, fair value	$ 357,800	$ 736,200
Amortized cost of callable debt securities	195,400
Fair value of callable debt securities	$ 189,700
Number of individual name issuer trust preferred securities in a continuous unrealized loss position total | security	71	57
Unrealized losses of securities in a continuous unrealized loss position total	$ 13,535	$ 15,841
Minimum [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Callable debt securities, maturity period	5 months
Callable debt securities, call feature period	1 month
Maximum [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Callable debt securities, maturity period	19 years
Callable debt securities, call feature period	4 years
Individual name issuer trust preferred debt securities [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Number of individual name issuer trust preferred securities in a continuous unrealized loss position total | security	7	10
Number of companies issuing securities in continuous unrealized loss position | security	5
Amortized cost of trust preferred securities of individual name issuers that are below investment grade	$ 6,100
Unrealized losses of trust preferred securities of individual name issuers that are below investment grade	509
Unrealized losses of securities in a continuous unrealized loss position total	$ 1,122	$ 3,115
Corporate bonds [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Number of individual name issuer trust preferred securities in a continuous unrealized loss position total | security	6	2
Unrealized losses of securities in a continuous unrealized loss position total	$ 805	$ 5