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Debt and Credit Facility - Schedule of Carrying Amounts of Borrowings (Details) - USD ($) | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2017 | Sep. 30, 2017 | Dec. 31, 2016
Debt Instrument [Line Items] |  |  |
Debt, Long-term and Short-term, Combined Amount | $ 33,542,000,000 |  | $ 26,346,000,000
Less current portion | 2,747,000,000 |  | 0
Total long-term debt, net | $ 30,795,000,000 |  | 26,346,000,000
Senior Unsecured Notes Due in September 2018 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 1.85% |  |
Senior Unsecured Notes | $ 999,000,000 |  | 998,000,000
2017 Senior Unsecured Notes Due in September 2018 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Senior Unsecured Notes | $ 749,000,000 |  | 0
Debt Instrument, Face Amount |  | $ 750,000,000 |
2017 Senior Unsecured Notes Due in September 2018 [Member] | London Interbank Offered Rate (LIBOR) [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Basis Spread on Variable Rate | 0.17% |  |
2017 Senior Unsecured Notes Due in March 2019 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Senior Unsecured Notes | $ 748,000,000 |  | 0
2017 Senior Unsecured Notes Due in March 2019 [Member] | London Interbank Offered Rate (LIBOR) [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Basis Spread on Variable Rate | 0.22% |  |
Senior Unsecured Notes Due in April 2019 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 2.05% |  |
Senior Unsecured Notes | $ 499,000,000 |  | 499,000,000
Term Loan Due May 2019 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term Line of Credit | $ 0 |  | 311,000,000
2017 Senior Unsecured Notes Due in September 2019 with Fixed Rate [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 1.85% | 1.85% |
Senior Unsecured Notes | $ 997,000,000 |  | 0
Debt Instrument, Face Amount |  | $ 1,000,000,000.0 |
2017 Senior Unsecured Notes Due in September 2019 with Floating Rate [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Senior Unsecured Notes | $ 499,000,000 |  | 0
Debt Instrument, Face Amount |  | $ 500,000,000 |
2017 Senior Unsecured Notes Due in September 2019 with Floating Rate [Member] | London Interbank Offered Rate (LIBOR) [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Basis Spread on Variable Rate | 0.25% |  |
Senior Unsecured Notes Due In February 2020 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 2.35% |  |
Senior Unsecured Notes | $ 499,000,000 |  | 498,000,000
Senior Unsecured Notes Due in September 2020 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 2.55% |  |
Senior Unsecured Notes | $ 1,994,000,000 |  | 1,991,000,000
Term Loan Due October 2020 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term Line of Credit | $ 998,000,000 |  | 0
Senior Unsecured Notes Due April 2021 Member |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 4.50% |  |
Senior Unsecured Notes | $ 995,000,000 |  | 994,000,000
Senior Unsecured Notes Due December 2021 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 4.40% |  |
Senior Unsecured Notes | $ 1,246,000,000 |  | 1,245,000,000
Senior Unsecured Notes Due in March 2022 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 1.95% |  |
Senior Unsecured Notes | $ 497,000,000 |  | 497,000,000
Senior Unsecured Notes Due in September 2022 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 3.25% |  |
Senior Unsecured Notes | $ 996,000,000 |  | 995,000,000
Term Loan Due October 2022 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term Line of Credit | $ 2,497,000,000 |  | 0
Senior Unsecured Notes Due in September 2023 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 2.50% |  |
Senior Unsecured Notes | $ 745,000,000 |  | 744,000,000
Senior Unsecured Notes Due in April 2024 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 3.70% |  |
Senior Unsecured Notes | $ 1,742,000,000 |  | 1,741,000,000
Senior Unsecured Notes Due in February 2025 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 3.50% |  |
Senior Unsecured Notes | $ 1,744,000,000 |  | 1,743,000,000
Senior Unsecured Notes Due in March 2026 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 3.65% |  |
Senior Unsecured Notes | $ 2,729,000,000 |  | 2,726,000,000
Senior Unsecured Notes Due in March 2027 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 2.95% |  |
Senior Unsecured Notes | $ 1,244,000,000 |  | 1,243,000,000
Senior Unsecured Notes Due in September 2035 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 4.60% |  |
Senior Unsecured Notes | $ 990,000,000 |  | 989,000,000
Senior Unsecured Notes Due in September 2036 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 4.00% |  |
Senior Unsecured Notes | $ 740,000,000 |  | 739,000,000
Senior Unsecured Notes Due December 2041 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 5.65% |  |
Senior Unsecured Notes | $ 995,000,000 |  | 995,000,000
Senior Unsecured Notes Due in April 2044 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 4.80% |  |
Senior Unsecured Notes | $ 1,733,000,000 |  | 1,732,000,000
Senior Unsecured Notes Due in February 2045 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 4.50% |  |
Senior Unsecured Notes | $ 1,730,000,000 |  | 1,729,000,000
Senior Unsecured Notes Due in March 2046 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 4.75% |  |
Senior Unsecured Notes | $ 2,215,000,000 |  | 2,214,000,000
Senior Unsecured Notes Due in March 2047 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 4.15% |  |
Senior Unsecured Notes | $ 1,723,000,000 |  | 1,723,000,000
Term Loan Due October 2018 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Line of Credit, Current | $ 999,000,000 |  | $ 0

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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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