Stock-based Compensation (Summary of Stock Option Activity) (Details) - Equity Option - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of shares under the plans:
Outstanding and exercisable at beginning of year, shares	0	0	7,500
Granted, shares			0
Canceled, shares			0
Exercised, shares			(7,500)
Outstanding and exercisable at end of year, shares	0	0	0
Weighted average exercise price (usd per share)			$ 9.08
Option intrinsic value			$ 253