Investments in Unconsolidated Joint Ventures - Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Schedule of Equity Method Investments [Line Items]
Revenues	$ 342,714	$ 249,207	$ 932,792	$ 701,070
Cost of sales	(321,390)	(234,444)	(877,005)	(656,813)
Operating income (loss)	21,324	14,763	55,787	44,257
Unconsolidated joint venture income	1,435	1,018	3,810	1,781
Joint Ventures
Schedule of Equity Method Investments [Line Items]
Revenues	5,397	3,100	14,675	6,634
Cost of sales	(2,521)	(1,453)	(7,043)	(3,459)
Operating income (loss)	$ 2,876	$ 1,647	$ 7,632	$ 3,175