Segment Information - Eliminations Footnote (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Operating income (loss)
Gross profit	$ 236,036	$ 187,042
Assets elimination
Accounts receivable	689,201		$ 613,605
Other	34,823		36,501
Total assets	6,391,642		$ 6,202,082
Eliminations
Operating income (loss)
Gross profit	(3,200)	$ 3,800
Assets elimination
Accounts receivable	(91,600)
Elimination of intra-company debt	(6,800)
Other	(6,600)
Total assets	$ (105,000)