Debt, Credit Facilities (Details) CAD in Millions		1 Months Ended	6 Months Ended
		Jul. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 CAD	Jun. 30, 2016 USD ($)	Dec. 31, 2015 CAD	Dec. 31, 2015 USD ($)
U S Revolver [Member] | Credit Facilities [Member]
Line of Credit Facility
Line of credit facility, maximum borrowing capacity						$ 3,000,000,000
Line of credit facility, expiration date			Nov. 30, 2020
Amount outstanding						0		$ 0
Line of credit facility, remaining borrowing capacity						2,947,000,000
Credit Facilities (Textual)
Line of credit facility, accordion feature, higher borrowing capacity option						4,500,000,000
U S Revolver Letter of Credit [Member] | Credit Facilities [Member]
Line of Credit Facility
Line of credit facility, maximum borrowing capacity						2,000,000,000
Amount outstanding						53,000,000
VLP Revolver [Member] | Credit Facilities [Member]
Line of Credit Facility
Line of credit facility, maximum borrowing capacity						750,000,000
Line of credit facility, expiration date			Nov. 30, 2020
Amount outstanding						314,000,000
Line of credit facility, remaining borrowing capacity						436,000,000
Credit Facilities (Textual)
Line of credit facility, accordion feature, higher borrowing capacity option						$ 1,000,000,000
Line of credit facility, interest rate at period end					1.75%	1.75%
Borrowings from long-term lines of credit			$ 139,000,000	$ 200,000,000
Repayments of long-term lines of credit			$ 0	$ 0
VLP Revolver Letter of Credit [Member] | Credit Facilities [Member]
Line of Credit Facility
Line of credit facility, maximum borrowing capacity						$ 100,000,000
Amount outstanding						0
Canadian Revolver [Member] | Credit Facilities [Member]
Line of Credit Facility
Line of credit facility, maximum borrowing capacity | CAD					CAD 50
Line of credit facility, expiration date			Nov. 30, 2016
Amount outstanding | CAD					0		CAD 0
Line of credit facility, remaining borrowing capacity | CAD					40
Canadian Revolver Letter of Credit [Member] | Credit Facilities [Member]
Line of Credit Facility
Amount outstanding | CAD					CAD 10
A/R Sales Facility [Member] | Credit Facilities [Member]
Line of Credit Facility
Line of credit facility, maximum borrowing capacity	[1]					1,400,000,000
Line of credit facility, expiration date			Jul. 31, 2016
Amount outstanding						100,000,000
Line of credit facility, remaining borrowing capacity						1,110,000,000
Credit Facilities (Textual)
Line of credit facility, current borrowing capacity						1,200,000,000
A/R Sales Facility [Member] | Credit Facilities [Member] | Subsequent Event [Member]
Line of Credit Facility
Line of credit facility, maximum borrowing capacity		$ 1,300,000,000
Line of credit facility, expiration date		Jul. 19, 2017
Committed Letter of Credit Facility [Member] | Credit Facilities [Member]
Line of Credit Facility
Line of credit facility, maximum borrowing capacity						275,000,000
Amount outstanding						16,000,000
Line of credit facility, remaining borrowing capacity						259,000,000
Committed Letter of Credit Facility Expires June 2016 [Member] | Credit Facilities [Member]
Line of Credit Facility
Line of credit facility, expiration date	[2]		Jun. 30, 2016
Committed Letter of Credit Facility Expires June 2016 [Member] | Credit Facilities [Member] | Subsequent Event [Member]
Line of Credit Facility
Line of credit facility, expiration date		Jun. 30, 2017
Committed Letter of Credit Facility Expires November 2016 [Member] | Credit Facilities [Member]
Line of Credit Facility
Line of credit facility, expiration date			Nov. 30, 2016
Uncommitted Letter of Credit Facility [Member]
Line of Credit Facility
Line of credit facility, maximum borrowing capacity						700,000,000
Amount outstanding						189,000,000
Line of credit facility, remaining borrowing capacity						$ 511,000,000

[1] As of June 30, 2016, the actual availability under the accounts receivable sales facility fell below the facility borrowing capacity to $1.2 billion primarily due to a decrease in eligible trade receivables as a result of the current market price environment for the finished products that we produce.

[2] In July 2016, we amended one of our committed letter of credit facilities to extend the maturity date from June 2016 to June 2017.