Consolidated Statements of Stockholders' Equity (Unaudited) - 3 months ended Mar. 31, 2017 - 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 at Dec. 31, 2016	$ 480,021	$ 1,282	$ (471,311)	$ 655,629	$ 294,925	$ (504)
Balance, Shares at Dec. 31, 2016		128,191	74,147
Net income	24,874				24,874
Other comprehensive income	180					180
Share repurchases	(2,271)		$ (2,271)
Share repurchases, Shares			176
Stock options exercised	$ 2,453	$ 3		2,450
Stock options exercised, Shares	335	335
Share-based compensation	$ 1,375	$ 1		1,374
Share-based compensation, Shares		70
Business acquisitions	633			633
Business acquisitions, Shares		47
Balance, Amount at Mar. 31, 2017	$ 507,265	$ 1,286	$ (473,582)	$ 660,086	$ 319,799	$ (324)
Balance, Shares at Mar. 31, 2017		128,643	74,323