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Debt - Narrative (Details) CAD in Millions | 3 Months Ended | 12 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Sep. 30, 2015 USD ($) | Dec. 31, 2016 USD ($) credit_facility | Dec. 31, 2015 USD ($) | Dec. 31, 2016 CAD | Dec. 31, 2016 EUR (€) | May 27, 2016 USD ($) | Mar. 01, 2016 USD ($) | Nov. 13, 2015 USD ($) | May 20, 2015 USD ($)
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Number of committed credit facilities | credit_facility |  | 2 |  |  |  |  |  |  |
Weighted average commercial paper outstanding |  | $ 265,000,000 | $ 402,000,000 |  |  |  |  |  |
Senior Notes | 3.125% Senior Notes due May 2016 |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt face value |  |  |  |  |  | $ 500,000,000 |  |  |
Interest rate on debt |  | 3.125% |  | 3.125% | 3.125% |  |  |  |
Senior Notes | 3.875% Senior Notes due December 2025 |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt face value |  |  |  |  |  |  | $ 750,000,000 |  |
Interest rate on debt |  | 3.875% |  | 3.875% | 3.875% |  |  |  |
Senior Notes | 2.80% Senior Notes due March 2021 |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt face value |  |  |  |  |  |  |  | $ 400,000,000 |
Interest rate on debt |  | 2.80% |  | 2.80% | 2.80% |  |  |  |
Senior Notes | 4.75% Senior Notes due May 2045 |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt face value |  |  |  |  |  |  |  |  | $ 600,000,000
Interest rate on debt |  | 4.75% |  | 4.75% | 4.75% |  |  |  |
Senior Notes | 4.76% Senior Notes due March 2018 (CAD 375M) |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt face value | CAD |  |  |  | CAD 375 |  |  |  |  |
Interest rate on debt |  | 4.76% |  | 4.76% | 4.76% |  |  |  |
Unsecured Debt | 4.76% Senior Notes due March 2018 (CAD 375M) |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Interest rate on debt |  | 4.76% |  | 4.76% | 4.76% |  |  |  |
Commercial Paper |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Weighted-average interest rates |  | 0.22% | 0.50% |  |  |  |  |  |
Senior Notes | 3.50% Senior Notes due September 2015 |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Interest rate on debt | 3.50% |  |  |  |  |  |  |  |
Extinguishment of debt | $ 600,000,000 |  |  |  |  |  |  |  |
Credit Facility Expiring March 2017 |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
New credit and loan facility |  | $ 400,000,000 |  |  |  |  |  |  |
Long-term commercial paper |  | 0 |  |  |  |  |  |  |
Credit Facility Expiring February 2021 |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
New credit and loan facility |  | 900,000,000 |  |  |  |  |  |  |
Long-term commercial paper |  | 0 |  |  |  |  |  |  |
Commercial Paper | Line of Credit |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Long-term commercial paper |  | 329,200,000 | $ 50,000,000 |  |  |  |  |  |
Commercial Paper | US Commercial Paper Program |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
New credit and loan facility |  | $ 900,000,000 |  |  |  |  |  |  |
Commercial Paper | European Multi-Currency Commercial Paper Program |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
New credit and loan facility | € |  |  |  |  | € 300,000,000 |  |  |  |

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- Definition The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement. + References 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(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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