Consolidated Statements of Stockholders' Equity (Unaudited) - 9 months ended Sep. 30, 2018 - USD ($) shares in Thousands, $ in Thousands	Total	Previously Reported [Member]	Cumulative Effect Adjustment [Member]	Common Stock [Member]	Common Stock [Member] Previously Reported [Member]	Treasury Stock [Member]	Treasury Stock [Member] Previously Reported [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] Previously Reported [Member]	Retained Earnings [Member]	Retained Earnings [Member] Previously Reported [Member]	Retained Earnings [Member] Cumulative Effect Adjustment [Member]	Accumulated Other Comprehensive (Loss) Gain [Member]	Accumulated Other Comprehensive (Loss) Gain [Member] Previously Reported [Member]
Balance, Amount at Dec. 31, 2017	$ 530,879	$ 530,879	$ 1,622		$ 1,301		$ (491,046)		$ 675,504		$ 345,302	$ 1,622		$ (182)
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 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	62,543									62,543
Other comprehensive income	343												343
Share repurchases	(8,121)					$ (8,121)
Share repurchases, Shares						379
Restricted stock				$ 3				(3)
Restricted stock, Shares				272
Stock options exercised	$ 6,076			$ 8				6,068
Stock options exercised, Shares	840			840
Share-based compensation	$ 5,358							5,358
Business acquisitions	3,215			$ 2				3,213
Business acquisitions, Shares				169
Balance, Amount at Sep. 30, 2018	$ 601,915			$ 1,314		$ (499,167)		$ 690,140		$ 409,467			$ 161
Balance, Shares at Sep. 30, 2018				131,356		75,863