CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Other Comprehensive Income	Retained Earnings (Deficit)	Noncontrolling Interests
Balance, Stockholders Equity at Dec. 31, 2016	$ 461,142	$ 35	$ 537,472	$ (46,774)	$ 15	$ (30,545)	$ 939
Balance (in shares) at Dec. 31, 2016		35,253,577
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock - employee stock purchase plan	2,382		2,382
Issuance of stock - employee stock purchase plan (shares)		53,848
Issuance of stock - 401 (k) plan	8,223		8,223
Issuance of stock - 401 (k) plan (shares)		156,487
Issuance/(cancellation) of non-vested stock	0
Issuance/(cancellation) of non-vested stock (shares)		139,016
Exercise of stock options	4,554		4,554
Exercise of stock options (in shares)		144,206
Non-cash compensation	16,295		16,295
Tax benefit from stock options exercised and restricted stock vesting	448					448
Surrendered shares	(6,939)			(6,939)
Noncontrolling interest distribution	(216)						(216)
Assets contributed to equity investment	(146)		(146)				0
Net income	30,683					30,301	382
Balance, Stockholders Equity at Dec. 31, 2017	516,426	$ 35	568,780	(53,713)	15	204	1,105
Balance (in shares) at Dec. 31, 2017		35,747,134
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock - employee stock purchase plan	2,429		2,429
Issuance of stock - employee stock purchase plan (shares)		38,961
Issuance of stock - 401 (k) plan	9,232		9,232
Issuance of stock - 401 (k) plan (shares)		129,451
Issuance/(cancellation) of non-vested stock	0	$ 1	(1)
Issuance/(cancellation) of non-vested stock (shares)		174,044
Exercise of stock options	5,953		5,953
Exercise of stock options (in shares)		162,690
Non-cash compensation	17,887		17,887
Surrendered shares	(6,570)			(6,570)
Shares repurchased	(181,402)			(181,402)
Noncontrolling interest distribution	(1,090)						(1,090)
Repurchase of noncontrolling interest	(361)		(614)				253
Net income	120,129					119,346	783
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	87,068
Non-cash compensation	$ 25,040		25,040
Surrendered shares	(9,556)			(9,556)
Noncontrolling interest distribution	(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