Consolidated Statements of Stockholders' Equity (Unaudited) - 6 months ended Jun. 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	48,957									48,957
Other comprehensive income	288												288
Share repurchases	(4,409)					$ (4,409)
Share repurchases, Shares						219
Restricted stock				$ 4				(4)
Restricted stock, Shares				272
Stock options exercised	$ 4,425			$ 5				4,420
Stock options exercised, Shares	616			616
Share-based compensation	$ 3,850							3,850
Business acquisitions	3,214			$ 1				3,213
Business acquisitions, Shares				169
Balance, Amount at Jun. 30, 2018	$ 588,826			$ 1,311		$ (495,455)		$ 686,983		$ 395,881			$ 106
Balance, Shares at Jun. 30, 2018				131,132		75,703