Debt (Details) - USD ($) | Jan. 06, 2016 | Mar. 31, 2016 | Dec. 31, 2015 | Aug. 27, 2015 |
Debt Instrument [Line Items] | | | | |
Debt | | $ 7,979,000,000 | $ 7,976,000,000 | |
Unamortized Discount | | (24,000,000) | (24,000,000) | |
Debt Instrument, Unamortized Premium | | 19,000,000 | 113,000,000 | |
Total Debt, Net of Discount | | 7,936,000,000 | 8,029,000,000 | |
Capital Lease Obligations, Current | | (54,000,000) | (53,000,000) | |
Long-term Debt Due After One Year | | $ 7,882,000,000 | 7,976,000,000 | |
Term Loan Facility [Member] | | | | |
Debt Instrument [Line Items] | | | | |
Debt | $ 1,400,000,000 | | $ 0 | |
Debt stated rate | | | 0.00% | |
Debt instrument, maturity date | | Jan. 6, 2019 | | |
Revolving Credit Facility, due August 27, 2020 | | | | |
Debt Instrument [Line Items] | | | | |
Debt | | $ 0 | $ 0 | |
Debt stated rate | | 0.00% | 0.00% | |
Debt instrument, maturity date | | Aug. 27, 2020 | Aug. 27, 2020 | |
Revolving Credit Facility Maximum Borrowing Capacity | | $ 4,000,000,000 | | |
Credit facility fee rate basis points, minimum | | | | 0.10% |
Credit facility fee rate basis points, maximum | | | | 0.25% |
Credit facility aggregate short-term loans and letters of credit, maximum | | | | $ 500,000,000 |
Credit facility aggregate short-term loans and letters of credit, committed | | 450,000,000 | | |
Credit facility interest rate, Eurodollar rate plus, minimum | | | | 0.90% |
Credit facility interest rate, Eurodollar rate plus, maximum | | | | 1.50% |
Capital Lease and Other Obligations | | | | |
Debt Instrument [Line Items] | | | | |
Debt | | $ 390,000,000 | $ 403,000,000 | |
Debt stated rate | | 0.00% | 0.00% | |
Capital Lease Obligations, Current | | $ (54,000,000) | $ (53,000,000) | |
8.25% Senior Notes, due March 1, 2019 | | | | |
Debt Instrument [Line Items] | | | | |
Debt | | $ 1,000,000,000 | $ 1,000,000,000 | |
Debt stated rate | | 8.25% | 8.25% | |
Debt instrument, maturity date | | Mar. 1, 2019 | Mar. 1, 2019 | |
5.625% Senior Notes, due May 1, 2021 | | | | |
Debt Instrument [Line Items] | | | | |
Debt | | $ 379,000,000 | $ 693,000,000 | |
Debt stated rate | | 5.625% | 5.625% | |
Debt instrument, maturity date | | May 1, 2021 | May 1, 2021 | |
4.15% Senior Notes, due December 15, 2021 | | | | |
Debt Instrument [Line Items] | | | | |
Debt | | $ 1,000,000,000 | $ 1,000,000,000 | |
Debt stated rate | | 4.15% | 4.15% | |
Debt instrument, maturity date | | Dec. 15, 2021 | Dec. 15, 2021 | |
5.875% Senior Notes, due June 1, 2022 | | | | |
Debt Instrument [Line Items] | | | | |
Debt | | $ 18,000,000 | $ 597,000,000 | |
Debt stated rate | | 5.875% | 5.875% | |
Debt instrument, maturity date | | Jun. 1, 2022 | Jun. 1, 2022 | |
7.25% Senior Notes, due October 15, 2023 | | | | |
Debt Instrument [Line Items] | | | | |
Debt | | $ 100,000,000 | $ 100,000,000 | |
Debt stated rate | | 7.25% | 7.25% | |
Debt instrument, maturity date | | Oct. 15, 2023 | Oct. 15, 2023 | |
Unamortized Debt Issuance Expense | | $ (38,000,000) | $ (36,000,000) | |
5.875% Senior Notes, due June 1, 2024 | | | | |
Debt Instrument [Line Items] | | | | |
Debt | | $ 8,000,000 | $ 499,000,000 | |
Debt stated rate | | 5.875% | 5.875% | |
Debt instrument, maturity date | | Jun. 1, 2024 | Jun. 1, 2024 | |
3.90% Senior Notes, due November 15, 2024 | | | | |
Debt Instrument [Line Items] | | | | |
Debt | | $ 650,000,000 | $ 650,000,000 | |
Debt stated rate | | 3.90% | 3.90% | |
Debt instrument, maturity date | | Nov. 15, 2024 | Nov. 15, 2024 | |
8.00% Senior Notes, due April 1, 2027 | | | | |
Debt Instrument [Line Items] | | | | |
Debt | | $ 250,000,000 | $ 250,000,000 | |
Debt stated rate | | 8.00% | 8.00% | |
Debt instrument, maturity date | | Apr. 1, 2027 | Apr. 1, 2027 | |
6.00% Senior Notes, due March 1, 2041 | | | | |
Debt Instrument [Line Items] | | | | |
Debt | | $ 850,000,000 | $ 850,000,000 | |
Debt stated rate | | 6.00% | 6.00% | |
Debt instrument, maturity date | | Mar. 1, 2041 | Mar. 1, 2041 | |
5.25% Senior Notes, due November 15, 2043 | | | | |
Debt Instrument [Line Items] | | | | |
Debt | | $ 1,000,000,000 | $ 1,000,000,000 | |
Debt stated rate | | 5.25% | 5.25% | |
Debt instrument, maturity date | | Nov. 15, 2043 | Nov. 15, 2043 | |
5.05% Senior Notes, due November 15, 2044 | | | | |
Debt Instrument [Line Items] | | | | |
Debt | | $ 850,000,000 | $ 850,000,000 | |
Debt stated rate | | 5.05% | 5.05% | |
Debt instrument, maturity date | | Nov. 15, 2044 | Nov. 15, 2044 | |
7.25% Senior Debentures, due August 1, 2097 | | | | |
Debt Instrument [Line Items] | | | | |
Debt | | $ 84,000,000 | $ 84,000,000 | |
Debt stated rate | | 7.25% | 7.25% | |
Debt instrument, maturity date | | Aug. 1, 2097 | Aug. 1, 2097 | |
Revolving Credit Facility, due August 27, 2020 | Credit Facility [Member] | | | | |
Debt Instrument [Line Items] | | | | |
Proceeds from Lines of Credit | | $ 1,380,000,000 | | |
Debt stated rate | | 1.69% | | |
Credit facility fee rate basis points, minimum | 0.10% | | | |
Credit facility fee rate basis points, maximum | 0.75% | | | |
Debt Instrument, Term | 3 years | | | |
Revolving Credit Facility, due August 27, 2020 | Federal Funds Effective Swap Rate [Member] | Credit Facility [Member] | | | | |
Debt Instrument [Line Items] | | | | |
Debt instrument, variable rate | 0.50% | | | |
Revolving Credit Facility, due August 27, 2020 | London Interbank Offered Rate (LIBOR) [Member] | Credit Facility [Member] | | | | |
Debt Instrument [Line Items] | | | | |
Credit facility interest rate, Eurodollar rate plus, minimum | 1.00% | | | |
Credit facility interest rate, Eurodollar rate plus, maximum | 1.75% | | | |
Debt instrument, variable rate | 1.00% | | | |
Other Operating Income (Expense) [Member] | Revolving Credit Facility, due August 27, 2020 | Credit Facility [Member] | | | | |
Debt Instrument [Line Items] | | | | |
Gain on tendered offers | | $ 80,000,000 | | |