Long-Term Debt - Revolving Credit Facilities (Details) $ in Millions	Dec. 31, 2017 USD ($)
Line of Credit Facility [Line Items]
Availability under revolving credit facilities	$ 2,450
Revolving Credit Facility
Line of Credit Facility [Line Items]
Availability under revolving credit facilities	1,500
Pacific Revolving Credit Facility
Line of Credit Facility [Line Items]
Availability under revolving credit facilities	415
Other Revolving Credit Facilities
Line of Credit Facility [Line Items]
Availability under revolving credit facilities	$ 535

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant