Stock-Based Employee Compensation (Options Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Options
Outstanding, beginning balance (Options)	346,310
Granted (Options)	0
Exercised (Options)	(72,000)
Canceled (Options)	(1,586)
Outstanding, ending balance (Options)	272,724	346,310
Vested and expected to vest (Options)	272,724
Options Exercisable (Options)	272,724
Weighted-Average Exercise Price
Outstanding, beginning balance (Price per Share)	$ 32.82
Granted (Price per Share)	0.00
Exercised (Price per Share)	35.07
Canceled (Price per Share)	46.18
Outstanding, ending balance (Price per Share)	32.15	$ 32.82
Vested and expected to vest (Price per Share)	32.15
Options Exercisable (Price per Share)	$ 32.15
Weighted-Average Remaining Contractual Term
Outstanding, beginning balance (Years)	1 year 4 months 28 days	2 years 4 months 21 days
Outstanding, ending balance (Years)	1 year 4 months 28 days	2 years 4 months 21 days
Vested and expected to vest (Years)	1 year 4 months 28 days
Options Exercisable (Years)	1 year 4 months 28 days
Aggregate Intrinsic Value
Outstanding, beginning balance	$ 24,053	$ 17,221
Outstanding, ending balance	24,053	17,221
Vested and expected to vest	24,053
Options Exercisable	24,053
Total intrinsic value of stock options exercised	$ 4,500	$ 2,300	$ 13,800