Debt Debt (First Lien Notes) (Details) - USD ($) $ in Millions |
Dec. 31, 2015 |
Mar. 31, 2015 |
Dec. 31, 2014 |
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|---|---|---|---|---|---|---|---|---|
| Debt Instrument [Line Items] | ||||||||
| Long-term Debt | $ 11,292 | $ 11,122 | ||||||
| 2022 First Lien Notes [Member] | ||||||||
| Debt Instrument [Line Items] | ||||||||
| Long-term Debt | $ 746 | $ 745 | ||||||
| Debt Instrument, Interest Rate, Effective Percentage | [1] | 6.30% | 6.30% | |||||
| First Lien Notes 2023 [Member] | ||||||||
| Debt Instrument [Line Items] | ||||||||
| Long-term Debt | [2] | $ 573 | $ 840 | |||||
| Debt Instrument, Interest Rate, Effective Percentage | [1] | 8.00% | 8.00% | |||||
| 2024 First Lien Notes [Member] | ||||||||
| Debt Instrument [Line Items] | ||||||||
| Long-term Debt | $ 490 | $ 490 | ||||||
| Debt Instrument, Interest Rate, Effective Percentage | [1] | 6.00% | 6.00% | |||||
| Corporate Debt Securities [Member] | ||||||||
| Debt Instrument [Line Items] | ||||||||
| Long-term Debt | $ 1,809 | $ 2,075 | ||||||
| Early Redemption Amount [Member] | First Lien Notes 2023 [Member] | ||||||||
| Debt Instrument [Line Items] | ||||||||
| Long-term Debt | $ 147 | |||||||
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