CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY Statement - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Other Comprehensive Income	Retained Earnings	Noncontrolling Interests
Balance, Stockholders Equity at Dec. 31, 2019	$ 641,513	$ 37	$ 645,256	$ (251,241)	$ 15	$ 246,383	$ 1,063
Balance (in shares) at Dec. 31, 2019		36,638,021
Issuance of stock - employee stock purchase plan	1,686		1,686
Issuance of stock - employee stock purchase plan (shares)		11,358
Issuance of stock - 401(k) plan	3,057	$ 0	3,057
Issuance of stock - 401(k) plan (shares)		18,312
Issuance/(cancellation) of non-vested stock	0	$ 0	0
Issuance/(cancellation) of non-vested stock (shares)		84,884
Exercise of stock options	2,947		2,947
Exercise of stock options (in shares)		78,723
Non-cash compensation	12,634		12,634
Surrendered Shares	(6,384)			(6,384)
Noncontrolling interest distribution	(372)						(372)
Write-off of other comprehensive income	(15)				(15)
Net income	67,193					66,476	717
Balance, Stockholders Equity at Jun. 30, 2020	722,259	$ 37	665,580	(257,625)	0	312,859	1,408
Balance (in shares) at Jun. 30, 2020		36,831,298
Balance, Stockholders Equity at Mar. 31, 2020	680,144	$ 37	656,266	(255,291)	0	278,185	947
Balance (in shares) at Mar. 31, 2020		36,746,554
Issuance of stock - employee stock purchase plan	826		826
Issuance of stock - employee stock purchase plan (shares)		5,295
Issuance/(cancellation) of non-vested stock	0	$ 0	0
Issuance/(cancellation) of non-vested stock (shares)		29,461
Exercise of stock options	1,763		1,763
Exercise of stock options (in shares)		49,988
Non-cash compensation	6,725		6,725
Surrendered Shares	(2,334)			(2,334)
Noncontrolling interest distribution	(12)						(12)
Net income	35,147					34,674	473
Balance, Stockholders Equity at Jun. 30, 2020	722,259	$ 37	665,580	(257,625)	0	312,859	1,408
Balance (in shares) at Jun. 30, 2020		36,831,298
Balance, Stockholders Equity at Dec. 31, 2020	810,741	$ 38	698,287	(319,092)	0	429,991	1,517
Balance (in shares) at Dec. 31, 2020		37,470,212
Issuance of stock - employee stock purchase plan	1,961		1,961
Issuance of stock - employee stock purchase plan (shares)		8,262
Issuance/(cancellation) of non-vested stock	0	$ 0	0
Issuance/(cancellation) of non-vested stock (shares)		61,069
Exercise of stock options	623		623
Exercise of stock options (in shares)		13,812
Non-cash compensation	13,463		13,463
Surrendered Shares	(6,944)			(6,944)
Shares repurchased	(74,074)			(74,074)
Noncontrolling interest distribution	(794)						(794)
Net income	130,911					130,019	892
Balance, Stockholders Equity at Jun. 30, 2021	875,887	$ 38	714,334	(400,110)	0	560,010	1,615
Balance (in shares) at Jun. 30, 2021		37,553,355
Balance, Stockholders Equity at Mar. 31, 2021	789,574	$ 38	707,006	(398,752)	0	479,861	1,421
Balance (in shares) at Mar. 31, 2021		37,538,837
Issuance of stock - employee stock purchase plan	913		913
Issuance of stock - employee stock purchase plan (shares)		4,060
Issuance/(cancellation) of non-vested stock	0	$ 0	0
Issuance/(cancellation) of non-vested stock (shares)		4,068
Exercise of stock options	259		259
Exercise of stock options (in shares)		6,390
Non-cash compensation	6,156		6,156
Surrendered Shares	(170)			(170)
Shares repurchased	(1,188)			(1,188)
Noncontrolling interest distribution	(276)						(276)
Net income	80,619					80,149	470
Balance, Stockholders Equity at Jun. 30, 2021	$ 875,887	$ 38	$ 714,334	$ (400,110)	$ 0	$ 560,010	$ 1,615
Balance (in shares) at Jun. 30, 2021		37,553,355