Share-Based Compensation (Weighted-Average Assumptions Used in Estimating Grant Date Fair Values of Stock Option Awards) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Key assumptions used in estimating the grant date fair values of stock option awards granted
Total stock options granted	165,000	220,000	664,000
Stock Options
Key assumptions used in estimating the grant date fair values of stock option awards granted
Total stock options granted	165,000	220,000	664,000
Weighted-average grant date fair value (in dollars per share)	$ 7.67	$ 7.59	$ 11.09
Risk-free rate (as a percent)	1.20%	2.10%	2.60%
Expected life of options	6 years 3 months 18 days	6 years 1 month 6 days	5 years 9 months 18 days
Expected volatility (as a percent)	60.70%	39.40%	42.20%
Expected quarterly dividends	$ 0	$ 0	$ 0