Fair Value Measurements (Aggregate Fair Value, Contractual Balance, and Gain or Loss for Loans Held-For-Sale) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Aggregate fair value	$ 52,133	$ 81,830
Contractual balance	50,597	81,009
Unrealized gain (loss)	$ 1,536	$ 821