Consolidated Statements of Stockholders' Equity (Unaudited) - 9 months ended Sep. 30, 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	45,530				45,530
Other comprehensive income	233					233
Share repurchases, Shares			708
Restricted stock	(10,261)	$ 3	$ (10,261)	(3)
Restricted stock, Shares		292
Stock options exercised	$ 6,227	$ 9		6,218
Stock options exercised, Shares	889	889
Share-based compensation	$ 4,247			4,247
Business acquisitions	4,489	$ 3		4,486
Business acquisitions, Shares		312
Balance, Amount at Sep. 30, 2017	$ 530,486	$ 1,297	$ (481,572)	$ 670,577	$ 340,455	$ (271)
Balance, Shares at Sep. 30, 2017		129,684	74,855