Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative-effect adjustment	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Retained Earnings Cumulative-effect adjustment	Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss Cumulative-effect adjustment
Beginning balance (in shares) at Dec. 31, 2018			131,404	76,332
Beginning balance at Dec. 31, 2018	$ 593,663	$ 0	$ 1,314	$ (508,530)	$ 692,398	$ 408,963	$ (101)	$ (482)	$ 101
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	70,714					70,714
Other comprehensive income (loss)	(299)							(299)
Share repurchases (in shares)				1,210
Share repurchases	(25,300)			$ (25,300)
Indirect repurchase of shares for minimum tax withholding (in shares)				95
Indirect repurchase of shares for minimum tax withholding	(1,863)			$ (1,863)
Restricted stock (in shares)			228
Restricted stock	0		$ 2		(2)
Stock options exercised (in shares)			1,210
Stock options exercised	10,608		$ 12		10,596
Share-based compensation	7,254				7,254
Business acquisitions (in shares)			214
Business acquisitions	4,461		$ 3		4,458
Ending balance (in shares) at Dec. 31, 2019			133,056	77,637
Ending balance at Dec. 31, 2019	659,238		$ 1,331	$ (535,693)	714,704	479,576		(680)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	78,299					78,299
Other comprehensive income (loss)	(1,589)							(1,589)
Share repurchases (in shares)				2,311
Share repurchases	(57,564)			$ (57,564)
Indirect repurchase of shares for minimum tax withholding (in shares)				97
Indirect repurchase of shares for minimum tax withholding	(2,040)			$ (2,040)
Restricted stock (in shares)			25
Stock options exercised (in shares)			634
Stock options exercised	6,486		$ 6		6,480
Share-based compensation	8,869				8,869
Business acquisitions (in shares)			429
Business acquisitions	10,921		$ 4		10,917
Ending balance (in shares) at Dec. 31, 2020			134,144	80,045
Ending balance at Dec. 31, 2020	702,620		$ 1,341	$ (595,297)	740,970	557,875		(2,269)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	70,887					70,887
Other comprehensive income (loss)	1,302							1,302
Share repurchases (in shares)				3,012
Share repurchases	(96,382)			$ (96,382)
Indirect repurchase of shares for minimum tax withholding (in shares)				92
Indirect repurchase of shares for minimum tax withholding	(3,037)			$ (3,037)
Restricted stock (in shares)			80
Restricted stock	$ 0		$ 1		(1)
Stock options exercised (in shares)	647		647
Stock options exercised	$ 7,311		$ 7		7,304
Share-based compensation	11,407				11,407
Business acquisitions (in shares)			316
Business acquisitions	10,440		$ 3		10,437
Ending balance (in shares) at Dec. 31, 2021			135,187	83,149
Ending balance at Dec. 31, 2021	$ 704,548		$ 1,352	$ (694,716)	$ 770,117	$ 628,762		$ (967)