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 at Dec. 31, 2017	$ 860,630	$ 392	$ 454,286	$ 325,794	$ 80,158
Beginning Balance (in shares) at Dec. 31, 2017		39,085
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)
Stock Repurchased During Period, Shares		(205)
Stock Repurchased During Period, Value	(5,000)	$ (2)	(4,998)
Shares remitted to Company to satisfy employee tax obligations	(4,696)	$ (2)	(4,694)
Shares remitted to Company to satisfy employee tax obligations (in shares)		(186)
Stock based compensation expense	3,181	$ 5	3,176
Stock based compensation expense (in shares)		577
Ending Balance at Mar. 31, 2018	853,659	$ 393	447,770	334,122	71,374
Ending Balance (in shares) at Mar. 31, 2018		39,271
Beginning Balance at Dec. 31, 2017	860,630	$ 392	454,286	325,794	80,158
Beginning Balance (in shares) at Dec. 31, 2017		39,085
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	39,824
Ending Balance at Jun. 30, 2018	980,955	$ 392	448,656	356,577	175,330
Ending Balance (in shares) at Jun. 30, 2018		39,225
Beginning Balance at Mar. 31, 2018	853,659	$ 393	447,770	334,122	71,374
Beginning Balance (in shares) at Mar. 31, 2018		39,271
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)
Stock Repurchased During Period, Shares		(48)
Stock Repurchased During Period, Value	(1,121)	$ (1)	(1,120)
Stock based compensation expense	2,006		2,006
Stock based compensation expense (in shares)		2
Ending Balance at Jun. 30, 2018	980,955	$ 392	448,656	356,577	175,330
Ending Balance (in shares) at Jun. 30, 2018		39,225
Beginning Balance at Dec. 31, 2018	1,014,327	$ 387	445,545	417,390	151,005
Beginning Balance (in shares) at Dec. 31, 2018		38,722
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	(2,356)	$ (1)	(2,355)
Shares remitted to Company to satisfy employee tax obligations (in shares)		(166)
Stock based compensation expense	2,765	$ 2	2,763
Stock based compensation expense (in shares)		281
Ending Balance at Mar. 31, 2019	1,020,201	$ 388	445,953	425,509	148,351
Ending Balance (in shares) at Mar. 31, 2019		38,837
Beginning Balance at Dec. 31, 2018	1,014,327	$ 387	445,545	417,390	151,005
Beginning Balance (in shares) at Dec. 31, 2018		38,722
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	29,564
Ending Balance at Jun. 30, 2019	1,026,402	$ 388	447,910	435,960	142,144
Ending Balance (in shares) at Jun. 30, 2019		38,789
Beginning Balance at Mar. 31, 2019	1,020,201	$ 388	445,953	425,509	148,351
Beginning Balance (in shares) at Mar. 31, 2019		38,837
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	1,963		1,963
Stock based compensation expense (in shares)		(50)
Ending Balance at Jun. 30, 2019	1,026,402	$ 388	$ 447,910	$ 435,960	$ 142,144
Ending Balance (in shares) at Jun. 30, 2019		38,789
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Issued During Period, Value, Stock Options Exercised	2
APIC, Share-based Payment Arrangement, Recognition and Exercise	$ (6)