CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - 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, 2018	$ 482,633	$ 36	$ 603,666	$ (241,685)	$ 15	$ 119,550	$ 1,051
Balance (in shares) at Dec. 31, 2018		36,252,280
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock - employee stock purchase plan	3,187		3,187
Issuance of stock - employee stock purchase plan (shares)		30,483
Issuance of stock - 401 (k) plan	9,753		9,753
Issuance of stock - 401 (k) plan (shares)		79,056
Issuance/(cancellation) of non-vested stock	0	$ 1	(1)
Issuance/(cancellation) of non-vested stock (shares)		189,134
Exercise of stock options	3,611		3,611
Exercise of stock options (in shares)		87,068
Non-cash compensation	25,040		25,040
Surrendered shares	(9,556)			(9,556)
Noncontrolling interest distributions	(1,062)						(1,062)
Net income	127,907					126,833	1,074
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock - employee stock purchase plan	3,562		3,562
Issuance of stock - employee stock purchase plan (shares)		21,561
Issuance of stock - 401 (k) plan	3,057		3,057
Issuance of stock - 401 (k) plan (shares)		18,312
Issuance/(cancellation) of non-vested stock	0		0
Issuance/(cancellation) of non-vested stock (shares)		169,489
Exercise of stock options	6,325	$ 1	6,324
Exercise of stock options (in shares)		622,829
Non-cash compensation	26,730		26,730
Surrendered shares	(54,493)		13,358	(67,851)
Noncontrolling interest distributions	(1,122)						(1,122)
Write-off of other comprehensive income	(15)				(15)
Net income	185,184					183,608	1,576
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock - employee stock purchase plan	3,968		3,968
Issuance of stock - employee stock purchase plan (shares)		20,823
Issuance/(cancellation) of non-vested stock	0
Issuance/(cancellation) of non-vested stock (shares)		151,365
Exercise of stock options	$ 2,054	$ 0	2,054
Exercise of stock options (in shares)	32,468	32,468
Non-cash compensation	$ 23,809		23,809
Surrendered shares	(16,898)			(16,898)
Shares repurchased	(99,878)			(99,878)
Noncontrolling interest contributions	250						250
Noncontrolling interest distributions	(1,747)						(1,747)
Acquired noncontrolling interest	43,858						43,858
Net income	210,166					209,072	1,094
Balance, Stockholders Equity at Dec. 31, 2021	$ 976,323	$ 38	$ 728,118	$ (435,868)	$ 0	$ 639,063	$ 44,972
Balance (in shares) at Dec. 31, 2021		37,674,868