Related Party Transactions (Details 1) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Related Party Transaction [Line Items]
Sales	$ 1,004,072	$ 836,595	$ 993,662	$ 852,016	$ 1,113,055	$ 859,612	$ 1,064,244	$ 887,879	$ 3,686,345	$ 3,924,790	$ 4,198,495
Gross profit	84,836	$ 69,671	$ 87,834	$ 76,458	103,694	$ 77,015	$ 97,042	$ 67,755	318,799	345,506	375,838
Net income (loss)									42,609	14,470	(11,322)
Current assets	999,211				1,058,126				999,211	1,058,126
Current liabilities	738,716				799,776				738,716	799,776
Noncontrolling interests	822,899				790,697				822,899	790,697	783,739	$ 824,049
Subsidiaries
Related Party Transaction [Line Items]
Sales									6,080,795	6,579,413	6,868,257
Gross profit									217,629	188,350	250,847
Income from continuing operations									50,937	12,288	85,220
Net income (loss)									42,970	6,445	81,368
Current assets	1,045,124				898,081				1,045,124	898,081	1,236,171
Non-current assets	538,671				565,416				538,671	565,416	500,637
Current liabilities	802,161				665,387				802,161	665,387	796,816
Non-current liabilities	309,649				359,816				309,649	359,816	342,075
Noncontrolling interests	$ 0				$ 3,628				$ 0	$ 3,628	$ 11,716