Consolidated Statements of Stockholders' Equity (Unaudited) - 9 months ended Sep. 30, 2016 - 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, 2015	$ 427,948	$ 1,262	$ (462,167)	$ 634,626	$ 254,860	$ (633)
Balance, Shares at Dec. 31, 2015		126,182	73,228
Net income	40,751				40,751
Other comprehensive loss	(291)					(291)
Share repurchases	(7,957)		$ (7,957)
Share repurchases, Shares			811
Restricted stock		$ 4		(4)
Restricted stock, Shares		301
Stock options exercised	$ 5,258	$ 6		5,252
Stock options exercised, Shares	749	749
Share-based compensation	$ 4,332			4,332
Tax benefit from employee share plans	830			830
Business acquisitions	3,815	$ 4		3,811
Business acquisitions, Shares		372
Balance, Amount at Sep. 30, 2016	$ 474,686	$ 1,276	$ (470,124)	$ 648,847	$ 295,611	$ (924)
Balance, Shares at Sep. 30, 2016		127,604	74,039