Unconsolidated Joint Ventures - Income Statement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Revenues	$ 147,447	$ 233,219	$ 409,881
Cost of sales and expenses	(147,976)	(207,028)	(344,687)
Net (loss) income of unconsolidated joint ventures	(529)	26,191	65,194
Equity in net income of unconsolidated joint ventures reflected in the accompanying consolidated statements of operations	$ 866	$ 7,691	$ 13,767