Condensed Consolidated Statements of Changes in Equity (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	Class A Common Stock	Class B Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Non-Controlling Interests
Adoption of Accounting Standard	$ (6,696)					$ (6,696)
Beginning Balance at Dec. 31, 2017	422,454	$ 186		$ (2,302)	$ 23,891	(185,991)	$ 155	$ 586,515
Beginning Balance (in shares) at Dec. 31, 2017		18,599,454	221	(60,333)
Net Income (Loss)	6,729					5,236		1,493
Other Comprehensive Income (Loss)	769						404	365
Dividends Declared ($0.05 Per Share of Class A Common Stock)	(967)					(967)
Equity-Based Compensation	37,062				25,666			11,396
Forfeiture Liability for Equity Awards	91				91
Net Share Settlement	(19,468)				(19,468)
Deliveries of Vested Shares of Common Stock		$ 11			(11)
Deliveries of Vested Shares of Common Stock (in shares)		1,135,047
Change in Ownership Interest	(24,078)				81,350			(105,428)
Change in Ownership Interest (in shares)			(6)
Treasury Stock Purchases	(3,890)			$ (3,890)
Treasury Stock Purchases (in shares)				(81,810)
Ending Balance at Mar. 31, 2018	412,006	$ 197		$ (6,192)	111,519	(188,418)	559	494,341
Ending Balance (in shares) at Mar. 31, 2018		19,734,501	215	(142,143)
Beginning Balance at Dec. 31, 2017	422,454	$ 186		$ (2,302)	23,891	(185,991)	155	586,515
Beginning Balance (in shares) at Dec. 31, 2017		18,599,454	221	(60,333)
Net Income (Loss)	17,749
Other Comprehensive Income (Loss)	(462)
Ending Balance at Jun. 30, 2018	417,876	$ 213		$ (28,029)	86,191	(182,588)	(73)	542,162
Ending Balance (in shares) at Jun. 30, 2018		21,261,616	213	(539,127)
Beginning Balance at Mar. 31, 2018	412,006	$ 197		$ (6,192)	111,519	(188,418)	559	494,341
Beginning Balance (in shares) at Mar. 31, 2018		19,734,501	215	(142,143)
Net Income (Loss)	11,020					6,945		4,075
Other Comprehensive Income (Loss)	(1,231)						(632)	(599)
Dividends Declared ($0.05 Per Share of Class A Common Stock)	(1,115)					(1,115)
Tax Distributions	(15)							(15)
Equity-Based Compensation	27,092				15,774			11,318
Forfeiture Liability for Equity Awards	18				18
Net Share Settlement	(1,584)				(1,584)
Deliveries of Vested Shares of Common Stock		$ 16			(16)
Deliveries of Vested Shares of Common Stock (in shares)		1,527,115
Change in Ownership Interest	(6,478)				(39,520)			33,042
Change in Ownership Interest (in shares)			(2)
Treasury Stock Purchases	(21,837)			$ (21,837)
Treasury Stock Purchases (in shares)				(396,984)
Ending Balance at Jun. 30, 2018	417,876	$ 213		$ (28,029)	86,191	(182,588)	(73)	542,162
Ending Balance (in shares) at Jun. 30, 2018		21,261,616	213	(539,127)
Beginning Balance at Dec. 31, 2018	487,749	$ 240		$ (67,172)	210,939	(169,836)	(627)	514,205
Beginning Balance (in shares) at Dec. 31, 2018		23,940,185	199	(1,353,398)
Net Income (Loss)	937					1,101		(164)
Other Comprehensive Income (Loss)	1,261						660	601
Dividends Declared ($0.05 Per Share of Class A Common Stock)	(1,188)					(1,188)
Equity-Based Compensation	34,973				23,884			11,089
Forfeiture Liability for Equity Awards	6				6
Net Share Settlement	(8,604)				(8,604)
Deliveries of Vested Shares of Common Stock		$ 11			(11)
Deliveries of Vested Shares of Common Stock (in shares)		1,088,396
Acquisition-Related Equity Issuance	2,287				1,889			398
Acquisition-Related Equity Issuance (in shares)		49,764
Change in Ownership Interest	(9,265)				53,377			(62,642)
Change in Ownership Interest (in shares)			1
Ending Balance at Mar. 31, 2019	508,156	$ 251		$ (67,172)	281,480	(169,923)	33	463,487
Ending Balance (in shares) at Mar. 31, 2019		25,078,345	200	(1,353,398)
Beginning Balance at Dec. 31, 2018	487,749	$ 240		$ (67,172)	210,939	(169,836)	(627)	514,205
Beginning Balance (in shares) at Dec. 31, 2018		23,940,185	199	(1,353,398)
Net Income (Loss)	10,963
Other Comprehensive Income (Loss)	$ 33
Treasury Stock Purchases (in shares)	(639,204)
Ending Balance at Jun. 30, 2019	$ 519,501	$ 251		$ (92,856)	278,053	(166,257)	(615)	500,925
Ending Balance (in shares) at Jun. 30, 2019		25,101,023	203	(1,992,602)
Beginning Balance at Mar. 31, 2019	508,156	$ 251		$ (67,172)	281,480	(169,923)	33	463,487
Beginning Balance (in shares) at Mar. 31, 2019		25,078,345	200	(1,353,398)
Net Income (Loss)	10,026					4,826		5,200
Other Comprehensive Income (Loss)	(1,228)						(648)	(580)
Dividends Declared ($0.05 Per Share of Class A Common Stock)	(1,160)					(1,160)
Tax Distributions	(20)							(20)
Equity-Based Compensation	30,676				19,465			11,211
Forfeiture Liability for Equity Awards	3				3
Net Share Settlement	(673)				(673)
Deliveries of Vested Shares of Common Stock (in shares)		22,678
Change in Ownership Interest	(595)				(22,222)			21,627
Change in Ownership Interest (in shares)			3
Treasury Stock Purchases	(25,684)			$ (25,684)
Treasury Stock Purchases (in shares)				(639,204)
Ending Balance at Jun. 30, 2019	$ 519,501	$ 251		$ (92,856)	$ 278,053	$ (166,257)	$ (615)	$ 500,925
Ending Balance (in shares) at Jun. 30, 2019		25,101,023	203	(1,992,602)