Derivative Instruments (Details 4) (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Sep. 30, 2015 |
Sep. 30, 2014 |
Sep. 30, 2015 |
Sep. 30, 2014 |
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| Derivative Instruments, Gain (Loss) [Line Items] | |||||||||||||
| Interest expense | $ 159 | $ 156 | $ 471 | $ 491 | |||||||||
| Interest Rate Swap [Member] | |||||||||||||
| Derivative Instruments, Gain (Loss) [Line Items] | |||||||||||||
| Gains (Loss) Recognized in OCI (Effective Portion) | [1],[2] | (4) | 11 | 4 | 2 | ||||||||
| Interest expense | 1 | 7 | 2 | 9 | |||||||||
| Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Swap [Member] | |||||||||||||
| Derivative Instruments, Gain (Loss) [Line Items] | |||||||||||||
| Interest expense | [1],[2],[3],[4] | $ (12) | $ (8) | $ (36) | $ (34) | ||||||||
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