Consolidated Statements of Stockholders' Equity (Unaudited) - 3 months ended Mar. 31, 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	21,768				21,768
Other comprehensive loss	(311)					(311)
Share repurchases	(6,137)		$ (6,137)
Share repurchases, Shares			633
Restricted stock		$ 1		(1)
Restricted stock, Shares		84
Stock options exercised	$ 796	$ 1		795
Stock options exercised, Shares	115	115
Share-based compensation	$ 1,409			1,409
Tax benefit from employee share plans	102			102
Business acquisitions	289			289
Business acquisitions, Shares		32
Balance, Amount at Mar. 31, 2016	$ 445,864	$ 1,264	$ (468,304)	$ 637,220	$ 276,628	$ (944)
Balance, Shares at Mar. 31, 2016		126,413	73,861