Debt Senior Unsecured Notes (Details) - USD ($) |
3 Months Ended | 12 Months Ended | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2015 |
Mar. 31, 2015 |
Sep. 30, 2014 |
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
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| Debt Instrument [Line Items] | |||||||||||||
| Long-term Debt | $ 11,292,000,000 | $ 11,292,000,000 | $ 11,122,000,000 | ||||||||||
| Gains (Losses) on Extinguishment of Debt | (40,000,000) | (346,000,000) | $ (144,000,000) | ||||||||||
| Senior Unsecured Notes 2023 [Member] | |||||||||||||
| Debt Instrument [Line Items] | |||||||||||||
| Long-term Debt | $ 1,250,000,000 | $ 1,250,000,000 | $ 1,250,000,000 | ||||||||||
| Debt Instrument, Interest Rate, Effective Percentage | [1] | 5.60% | 5.60% | 5.60% | |||||||||
| Debt Instrument, Face Amount | $ 1,250,000,000 | ||||||||||||
| Debt Instrument, Interest Rate, Stated Percentage | 5.375% | ||||||||||||
| Senior Unsecured Notes 2024 [Member] | |||||||||||||
| Debt Instrument [Line Items] | |||||||||||||
| Long-term Debt | $ 650,000,000 | $ 650,000,000 | $ 0 | ||||||||||
| Debt Instrument, Interest Rate, Effective Percentage | [1] | 5.70% | 5.70% | 0.00% | |||||||||
| Debt Instrument, Face Amount | $ 650,000,000 | ||||||||||||
| Debt Instrument, Interest Rate, Stated Percentage | 5.50% | ||||||||||||
| Deferred Finance Costs, Net | $ 9,000,000 | ||||||||||||
| Senior Unsecured Notes 2025 [Member] | |||||||||||||
| Debt Instrument [Line Items] | |||||||||||||
| Long-term Debt | $ 1,550,000,000 | $ 1,550,000,000 | $ 1,550,000,000 | ||||||||||
| Debt Instrument, Interest Rate, Effective Percentage | [1] | 5.90% | 5.90% | 5.90% | |||||||||
| Debt Instrument, Face Amount | $ 1,550,000,000 | ||||||||||||
| Debt Instrument, Interest Rate, Stated Percentage | 5.75% | ||||||||||||
| First Lien Notes 2023 [Member] | |||||||||||||
| Debt Instrument [Line Items] | |||||||||||||
| Long-term Debt | [2] | $ 573,000,000 | $ 573,000,000 | $ 840,000,000 | |||||||||
| Debt Instrument, Interest Rate, Effective Percentage | [3] | 8.00% | 8.00% | 8.00% | |||||||||
| Gains (Losses) on Extinguishment of Debt | $ (7,000,000) | (19,000,000) | |||||||||||
| First Lien Notes 2023 [Member] | Early Redemption Amount [Member] | |||||||||||||
| Debt Instrument [Line Items] | |||||||||||||
| Long-term Debt | $ 147,000,000 | ||||||||||||
| 2019, 2020 and 2021 First Lien Notes [Member] | |||||||||||||
| Debt Instrument [Line Items] | |||||||||||||
| Deferred Finance Costs, Net | $ 42,000,000 | ||||||||||||
| Gains (Losses) on Extinguishment of Debt | $ (340,000,000) | ||||||||||||
| Unsecured Debt [Member] | |||||||||||||
| Debt Instrument [Line Items] | |||||||||||||
| Long-term Debt | $ 3,450,000,000 | $ 3,450,000,000 | $ 2,800,000,000 | ||||||||||
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