Consolidated Statement of Stockholders' Equity - USD ($) $ in Thousands	Previously Reported [Member] Common Stock Common Class A	Previously Reported [Member] Common Stock Common Class B	Previously Reported [Member] Additional paid-in capital	Previously Reported [Member] Retained earnings	Previously Reported [Member] Accumulated other comprehensive income (loss), net of tax	Previously Reported [Member] Non-controlling interest	Previously Reported [Member]	Restatement Adjustment [Member] Common Stock Common Class A	Restatement Adjustment [Member] Common Stock Common Class B	Restatement Adjustment [Member] Additional paid-in capital	Restatement Adjustment [Member] Retained earnings	Restatement Adjustment [Member] Accumulated other comprehensive income (loss), net of tax	Restatement Adjustment [Member] Non-controlling interest	Restatement Adjustment [Member]	Common Stock Common Class A	Common Stock Common Class B	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income (loss), net of tax	Non-controlling interest	Total
Cumulative effect adjustment from change in accounting principle											$ (4,875)		$ (11,596)	$ (16,471)
Adjusted balance															$ 2		$ 446,209	$ (644)	$ (105)	$ (422,519)	$ 22,943
Beginning balance, Value at Dec. 31, 2015	$ 2		$ 446,209	$ 4,231	$ (105)	$ (410,923)	$ 39,414
Beginning balance, Shares at Dec. 31, 2015	17,584,351	1													17,584,351	1
Net income																		22,221		24,627	46,848
Distributions paid to non-controlling unitholders																				(17,927)	(17,927)
Equity-based compensation expense and related dividend equivalents, value																	2,330				2,330
Dividends paid to Class A common stockholders																		(10,578)			(10,578)
Change in accumulated other comprehensive (loss) income																			58	88	146
Payroll taxes related to net settled restricted stock units																	(516)				(516)
Payroll taxes related to net settled restricted stock units (in shares)															(13,639)
Issuance of Class A common stock, equity-based compensation plans, value																	101				101
Issuance of Class A common stock, equity-based compensation plans, shares															81,836
Other																	466				466
Ending balance, Value at Dec. 31, 2016								$ 2		$ 448,713	10,955	$ (47)	(415,782)	43,841
Ending balance, Shares at Dec. 31, 2016								17,652,548	1
Cumulative effect adjustment from change in accounting principle																	123	(44)		(51)	28
Net income																		10,238		21,577	31,815
Distributions paid to non-controlling unitholders																				(17,260)	(17,260)
Equity-based compensation expense and related dividend equivalents, value																	2,900	(53)			2,847
Equity-based compensation expense and related dividend equivalents, shares															58,426
Dividends paid to Class A common stockholders																		(12,740)			(12,740)
Change in accumulated other comprehensive (loss) income																			506	531	1,037
Payroll taxes related to net settled restricted stock units																	(816)				(816)
Payroll taxes related to net settled restricted stock units (in shares)															(13,983)
Other																	402				402
Ending balance, Value at Dec. 31, 2017								$ 2		$ 451,199	$ 8,400	$ 459	$ (410,934)	$ 49,126							49,126
Ending balance, Shares at Dec. 31, 2017								17,696,991	1						17,696,991	1
Net income																		27,044		23,321	50,365
Distributions paid to non-controlling unitholders																				(14,559)	(14,559)
Equity-based compensation expense and related dividend equivalents, value																	9,314	(113)			9,201
Equity-based compensation expense and related dividend equivalents, shares															73,462
Dividends paid to Class A common stockholders																		(14,193)			(14,193)
Change in accumulated other comprehensive (loss) income																			(131)	(122)	(253)
Payroll taxes related to net settled restricted stock units																	(895)				(895)
Payroll taxes related to net settled restricted stock units (in shares)															(16,037)
Other																	483				483
Ending balance, Value at Dec. 31, 2018															$ 2		$ 460,101	$ 21,138	$ 328	$ (402,294)	$ 79,275
Ending balance, Shares at Dec. 31, 2018															17,754,416	1