CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands		Total	Common Stock	Treasury	Additional Paid-In Capital	Retained Earnings	Noncontrolling Interest Non Redeemable
Beginning balance at Dec. 31, 2019		$ 1,507,251	$ 361	$ (60,060)	$ 949,321	$ 523,701	$ 93,928
Beginning balance (in shares) at Dec. 31, 2019			36,129,280	5,136,890
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	[1]	24,123				22,024	2,099
Acquired noncontrolling interest		2,880					2,880
Noncontrolling interest distributions		(2,093)					(2,093)
Purchase of additional controlling interest		(23,575)			(2,470)		(21,105)
Nonvested stock compensation		3,680			3,680
Issuance of vested stock		2	$ 2
Issuance of vested stock (in shares)			163,163
Treasury shares redeemed to pay income tax		(6,933)		$ (7,122)	189
Treasury shares redeemed to pay income tax (in shares)				59,390
Issuance of common stock under Employee Stock Purchase Plan (in shares)			4,663
Issuance of common stock under Employee Stock Purchase Plan		610			610
Ending balance at Mar. 31, 2020		1,505,945	$ 363	$ (67,182)	951,330	545,725	75,709
Ending balance (in shares) at Mar. 31, 2020			36,297,106	5,196,280
Beginning balance at Dec. 31, 2019		1,507,251	$ 361	$ (60,060)	949,321	523,701	93,928
Beginning balance (in shares) at Dec. 31, 2019			36,129,280	5,136,890
Ending balance at Jun. 30, 2020		1,558,103	$ 363	$ (68,654)	955,119	590,417	80,858
Ending balance (in shares) at Jun. 30, 2020			36,327,819	5,205,851
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to noncontrolling interest-redeemable		9,600
Beginning balance at Mar. 31, 2020		1,505,945	$ 363	$ (67,182)	951,330	545,725	75,709
Beginning balance (in shares) at Mar. 31, 2020			36,297,106	5,196,280
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	[1]	51,750				44,692	7,058
Noncontrolling interest distributions		(1,909)					(1,909)
Nonvested stock compensation		3,263			3,263
Issuance of vested stock (in shares)			19,846
Treasury shares redeemed to pay income tax		(1,139)		$ (950)	(189)
Treasury shares redeemed to pay income tax (in shares)				6,256
Exercise of options (in shares)			7,137	3,315
Exercise of options		(304)		$ (522)	218
Issuance of common stock under Employee Stock Purchase Plan (in shares)			3,730
Issuance of common stock under Employee Stock Purchase Plan		497			497
Ending balance at Jun. 30, 2020		1,558,103	$ 363	$ (68,654)	955,119	590,417	80,858
Ending balance (in shares) at Jun. 30, 2020			36,327,819	5,205,851
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to noncontrolling interest-redeemable		3,500
Beginning balance at Dec. 31, 2020		1,613,354	$ 364	$ (69,011)	962,120	635,297	84,584
Beginning balance (in shares) at Dec. 31, 2020			36,355,497	5,215,657
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	[2]	39,128				34,659	4,469
Noncontrolling interest distributions		(2,417)					(2,417)
Purchase of additional controlling interest		(142)			(81)		(61)
Sale of noncontrolling interest		138					138
Nonvested stock compensation		3,513			3,513
Issuance of vested stock		1	$ 1
Issuance of vested stock (in shares)			148,447
Treasury shares redeemed to pay income tax		$ (9,541)		$ (9,541)
Treasury shares redeemed to pay income tax (in shares)				51,221
Issuance of common stock under Employee Stock Purchase Plan (in shares)		3,204	3,204
Issuance of common stock under Employee Stock Purchase Plan		$ 649			649
Ending balance at Mar. 31, 2021		1,644,683	$ 365	$ (78,552)	966,201	669,956	86,713
Ending balance (in shares) at Mar. 31, 2021			36,507,148	5,266,878
Beginning balance at Dec. 31, 2020		1,613,354	$ 364	$ (69,011)	962,120	635,297	84,584
Beginning balance (in shares) at Dec. 31, 2020			36,355,497	5,215,657
Ending balance at Jun. 30, 2021		1,684,653	$ 365	$ (79,765)	969,897	707,599	86,557
Ending balance (in shares) at Jun. 30, 2021			36,525,831	5,272,902
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to noncontrolling interest-redeemable		6,183
Beginning balance at Mar. 31, 2021		1,644,683	$ 365	$ (78,552)	966,201	669,956	86,713
Beginning balance (in shares) at Mar. 31, 2021			36,507,148	5,266,878
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	[2]	42,875				37,643	5,232
Noncontrolling interest distributions		(4,660)					(4,660)
Purchase of additional controlling interest		(1,598)			(870)		(728)
Nonvested stock compensation		3,993			3,993
Issuance of vested stock (in shares)			15,531
Treasury shares redeemed to pay income tax		$ (1,213)		$ (1,213)
Treasury shares redeemed to pay income tax (in shares)				6,024
Issuance of common stock under Employee Stock Purchase Plan (in shares)		3,152	3,152
Issuance of common stock under Employee Stock Purchase Plan		$ 573			573
Ending balance at Jun. 30, 2021		1,684,653	$ 365	$ (79,765)	$ 969,897	$ 707,599	$ 86,557
Ending balance (in shares) at Jun. 30, 2021			36,525,831	5,272,902
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to noncontrolling interest-redeemable		$ 3,900

[1] Net income excludes net income attributable to noncontrolling interest-redeemable of $3.5 million and $9.6 million during the three and six months ended June 30, 2020. Noncontrolling interest-redeemable is reflected outside of permanent equity on the condensed consolidated balance sheets. See Note 8 of the Notes to Condensed Consolidated Financial Statements.

[2] Net income excludes net income attributable to noncontrolling interest-redeemable of $3.9 million and $6.2 million during the three and six months ended June 30, 2021. Noncontrolling interest-redeemable is reflected outside of permanent equity on the condensed consolidated balance sheets. See Note 8 of the Notes to Condensed Consolidated Financial Statements.