Investments in Unconsolidated Joint Ventures - Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Schedule of Equity Method Investments [Line Items]
Total operating revenue	$ 325,653	$ 254,695	$ 590,078	$ 451,863
Cost of sales	(304,470)	(235,348)	(555,615)	(422,369)
Operating income (loss)	21,183	19,347	34,463	29,494
Unconsolidated joint venture income	1,194	515	2,375	763
Joint Ventures
Schedule of Equity Method Investments [Line Items]
Total operating revenue	5,311	2,828	9,278	3,534
Cost of sales	(2,597)	(1,624)	(4,522)	(2,006)
Operating income (loss)	$ 2,714	$ 1,204	$ 4,756	$ 1,528