Consolidated Statements of Stockholders' Equity (Unaudited) - 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, 2018	$ 593,663	$ 1,314	$ (508,530)	$ 692,398	$ 408,963	$ (482)
Balance, Shares at Dec. 31, 2018		131,404	76,332
Cumulative impact of ASU 2018-02adoption					(101)	101
Net income	37,469				37,469
Other comprehensive income (loss)	81					81
Share repurchases	(11,558)		$ (11,558)
Share repurchases, Shares			580
Restricted Stock		$ 1		(1)
Restricted Stock, Shares		173
Stock options exercised	1,400	$ 2		1,398
Stock options exercised, Shares		189
Stock-based compensation	1,482			1,482
Business acquisitions	950	$ 1		949
Business acquisitions, Shares		47
Balance, Amount at Mar. 31, 2019	623,487	$ 1,318	$ (520,088)	696,226	446,331	(300)
Balance, Shares at Mar. 31, 2019		131,813	76,912
Balance, Amount at Dec. 31, 2019	659,238	$ 1,331	$ (535,693)	714,704	479,576	(680)
Balance, Shares at Dec. 31, 2019		133,056	77,637
Net income	36,848				36,848
Other comprehensive income (loss)	(1,252)					(1,252)
Share repurchases	(29,487)		$ (29,487)
Share repurchases, Shares			1,174
Stock options exercised	$ 1,013	$ 1		1,012
Stock options exercised, Shares	116	116
Stock-based compensation	$ 2,023			2,023
Business acquisitions	1,877			1,877
Business acquisitions, Shares		69
Balance, Amount at Mar. 31, 2020	$ 670,260	$ 1,332	$ (565,180)	$ 719,616	$ 516,424	$ (1,932)
Balance, Shares at Mar. 31, 2020		133,241	78,811