CONDENSED CONSOLIDATED STATEMENT OF EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Non- Controlling Interests
Beginning Balance (in shares) at Dec. 31, 2017		39,085
Beginning Balance at Dec. 31, 2017	$ 860,630	$ 392	$ 454,286	$ 325,794	$ 80,158
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	12,588			8,328	4,260
Cash contributions from members of consolidated entities	4,062				4,062
Cash distributions to members of consolidated entities	(17,106)				(17,106)
Repurchases of common stock (in shares)		(205)
Repurchases of common stock	(5,000)	$ (2)	(4,998)
Shares remitted to Company to satisfy employee tax obligations (in shares)		(186)
Shares remitted to Company to satisfy employee tax obligations	(4,696)	$ (2)	(4,694)
Stock based compensation expense (in shares)		577
Stock based compensation expense	3,181	$ 5	3,176
Ending Balance (in shares) at Mar. 31, 2018		39,271
Ending Balance at Mar. 31, 2018	853,659	$ 393	447,770	334,122	71,374
Beginning Balance (in shares) at Dec. 31, 2017		39,085
Beginning Balance at Dec. 31, 2017	860,630	$ 392	454,286	325,794	80,158
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	71,638
Ending Balance (in shares) at Sep. 30, 2018		38,967
Ending Balance at Sep. 30, 2018	997,827	$ 389	445,694	383,135	168,609
Beginning Balance (in shares) at Mar. 31, 2018		39,271
Beginning Balance at Mar. 31, 2018	853,659	$ 393	447,770	334,122	71,374
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	27,236			22,455	4,781
Cash contributions from members of consolidated entities	116,040				116,040
Cash distributions to members of consolidated entities	(16,865)				(16,865)
Repurchases of common stock (in shares)		(48)
Repurchases of common stock	(1,121)	$ (1)	(1,120)
Shares remitted to Company to satisfy employee tax obligations	0
Stock based compensation expense (in shares)		2
Stock based compensation expense	2,006		2,006
Ending Balance (in shares) at Jun. 30, 2018		39,225
Ending Balance at Jun. 30, 2018	980,955	$ 392	448,656	356,577	175,330
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	31,814			26,558	5,256
Cash contributions from members of consolidated entities	5,986				5,986
Cash distributions to members of consolidated entities	(17,963)				(17,963)
Repurchases of common stock (in shares)		(244)
Repurchases of common stock	(5,113)	$ (3)	(5,110)
Shares remitted to Company to satisfy employee tax obligations (in shares)		(12)
Shares remitted to Company to satisfy employee tax obligations	(258)		(258)
Stock based compensation expense (in shares)		(2)
Stock based compensation expense	2,406		2,406
Ending Balance (in shares) at Sep. 30, 2018		38,967
Ending Balance at Sep. 30, 2018	997,827	$ 389	445,694	383,135	168,609
Beginning Balance (in shares) at Dec. 31, 2018		38,722
Beginning Balance at Dec. 31, 2018	1,014,327	$ 387	445,545	417,390	151,005
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	15,134			8,119	7,015
Cash contributions from members of consolidated entities	1,389				1,389
Cash distributions to members of consolidated entities	(11,058)				(11,058)
Shares remitted to Company to satisfy employee tax obligations (in shares)		(166)
Shares remitted to Company to satisfy employee tax obligations	(2,356)	$ (1)	(2,355)
Stock based compensation expense (in shares)		281
Stock based compensation expense	2,765	$ 2	2,763
Ending Balance (in shares) at Mar. 31, 2019		38,837
Ending Balance at Mar. 31, 2019	1,020,201	$ 388	445,953	425,509	148,351
Beginning Balance (in shares) at Dec. 31, 2018		38,722
Beginning Balance at Dec. 31, 2018	1,014,327	$ 387	445,545	417,390	151,005
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	47,074
Ending Balance (in shares) at Sep. 30, 2019		38,800
Ending Balance at Sep. 30, 2019	1,032,363	$ 388	450,137	445,440	136,398
Beginning Balance (in shares) at Mar. 31, 2019		38,837
Beginning Balance at Mar. 31, 2019	1,020,201	$ 388	445,953	425,509	148,351
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	14,430			10,451	3,979
Cash contributions from members of consolidated entities	1,465				1,465
Cash distributions to members of consolidated entities	(11,651)				(11,651)
Stock based compensation expense (in shares)		(50)
Stock based compensation expense	1,963		1,963
Exercise of stock options (in shares)	2
Exercise of stock options	(6)		(6)
Ending Balance (in shares) at Jun. 30, 2019		38,789
Ending Balance at Jun. 30, 2019	1,026,402	$ 388	447,910	435,960	142,144
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	17,510			9,480	8,030
Cash distributions to members of consolidated entities	(13,776)				(13,776)
Stock based compensation expense (in shares)		4
Stock based compensation expense	2,233		2,233
Exercise of stock options (in shares)	7
Exercise of stock options	(6)		(6)
Ending Balance (in shares) at Sep. 30, 2019		38,800
Ending Balance at Sep. 30, 2019	$ 1,032,363	$ 388	$ 450,137	$ 445,440	$ 136,398