Condensed Consolidated Statement of Stockholder's Equity (USD $)	Total USD ($)	Additional paid-in capital USD ($)	Retained earnings USD ($)	Accumulated other comprehensive income USD ($)	Noncontrolling interest USD ($)	Common Class A USD ($)	Common Class B
Beginning balance, Value at Dec. 31, 2013	$ 15,539,000	$ 239,086,000	$ 1,506,000	$ 1,371,000	$ (226,425,000)	$ 1,000
Beginning balance, Shares at Dec. 31, 2013						11,607,971	1
Net income	36,362,000		11,063,000		25,299,000
Distributions paid to non-controlling unitholders	(16,329,000)				(16,329,000)
Share-based compensation	532,000	532,000
Dividends paid to Class A common stockholders	(2,173,000)		(2,173,000)
Change in accumulated other comprehensive income	(236,000)			(236,000)
Excess tax benefit realized on delivery of vested restricted stock units and exercise of stock options	179,000	179,000
Cancellation of vested restricted stock units to satisfy statutory tax withholding requirements, Value	(818,000)	(818,000)
Cancellation of vested restricted stock units to satisfy statutory tax withholding requirements, Shares	(30,519)					(30,519)
Exercise of stock options, Value	54,000	54,000
Exercise of stock options, Shares	15,000					15,000
Ending balance, Value at Sep. 30, 2014	$ 33,110,000	$ 239,033,000	$ 10,396,000	$ 1,135,000	$ (217,455,000)	$ 1,000
Ending balance, Shares at Sep. 30, 2014						11,592,452	1