Debt, Credit Facilities (Details)		3 Months Ended
	Apr. 01, 2016 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Mar. 31, 2016 CAD	Mar. 31, 2016 USD ($)	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					175,000,000
Line of credit facility, remaining borrowing capacity					575,000,000
Credit Facilities (Textual)
Line of credit facility, accordion feature, higher borrowing capacity option					1,000,000,000
Line of credit facility, interest rate during period		1.75%
Borrowings from long-term lines of credit		$ 0	$ 200,000,000
Repayments of long-term lines of credit		$ 0
VLP Revolver [Member] | Credit Facilities [Member] | Subsequent Event [Member]
Credit Facilities (Textual)
Borrowings from long-term lines of credit	$ 139,000,000
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 50,000,000
Line of credit facility, expiration date		Nov. 30, 2016
Amount outstanding | CAD				0		CAD 0
Line of credit facility, remaining borrowing capacity | CAD				40,000,000
Canadian Revolver Letter of Credit [Member] | Credit Facilities [Member]
Line of Credit Facility
Amount outstanding | CAD				CAD 10,000,000
A/R Sales Facility [Member] | Credit Facilities [Member]
Line of Credit Facility
Line of credit facility, maximum borrowing capacity					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					974,000,000
Credit Facilities (Textual)
Line of credit facility, current borrowing capacity					1,100,000,000
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		Jun. 30, 2016
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					61,000,000
Line of credit facility, remaining borrowing capacity					$ 639,000,000