Consolidated Statements of Stockholders' Equity (Unaudited) - 3 months ended Mar. 31, 2018 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Balance, Amount (Previously Reported [Member]) at Dec. 31, 2017	$ 530,879	$ 1,301	$ (491,046)	$ 675,504	$ 345,302	$ (182)
Balance, Amount (Cumulative Effect Adjustment [Member]) at Dec. 31, 2017	1,622				1,622
Balance, Amount at Dec. 31, 2017	530,879
Balance, Amount (Accounting Standards Update 2014-09 [Member]) at Dec. 31, 2017	532,501	$ 1,301	$ (491,046)	675,504	346,924	(182)
Balance, Shares (Previously Reported [Member]) at Dec. 31, 2017		130,075	75,484
Balance, Shares (Accounting Standards Update 2014-09 [Member]) at Dec. 31, 2017		130,075	75,484
Net income	35,851				35,851
Other comprehensive income	114					114
Share repurchases	(558)		$ (558)
Share repurchases, Shares			31
Stock options exercised	$ 2,271	$ 4		2,267
Stock options exercised, Shares	339	339
Share-based compensation	$ 1,437			1,437
Share-based compensation, Shares		56
Balance, Amount at Mar. 31, 2018	$ 571,616	$ 1,305	$ (491,604)	$ 679,208	$ 382,775	$ (68)
Balance, Shares at Mar. 31, 2018		130,470	75,515