Segment Information - Eliminations Footnote (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating income (loss)
Gross profit	$ 144,207	$ 228,726	$ 171,743	$ 187,042	$ 291,624	$ 288,512	$ 222,771	$ 163,304	$ 731,718	$ 966,211	$ 719,144
Assets elimination
Accounts receivable	613,605				902,825				613,605	902,825
Other	36,501				55,164				36,501	55,164
Total assets	6,202,082				7,233,159				6,202,082	7,233,159	5,888,534
Liabilities elimination
Accounts payable	283,355				511,056				283,355	511,056
Liabilities	3,530,631				4,311,292				3,530,631	4,311,292	3,276,165
Eliminations
Operating income (loss)
Gross profit									5,000	4,400	(600)
Assets elimination
Accounts receivable	(74,900)				(125,100)				(74,900)	(125,100)	(69,000)
Elimination of intra-company debt	(6,200)				(7,100)				(6,200)	(7,100)	(8,000)
Other	(3,400)				(8,400)				(3,400)	(8,400)	(12,700)
Total assets	(84,480)				(140,642)				(84,480)	(140,642)	(89,724)
Liabilities elimination
Accounts payable	(74,900)				(125,200)				(74,900)	(125,200)	(69,000)
Elimination of intra-company debt	(6,200)				(7,100)				(6,200)	(7,100)	(8,000)
Other	1,900				1,600				1,900	1,600	(400)
Liabilities	$ (79,221)				$ (130,735)				$ (79,221)	$ (130,735)	$ (77,359)