Derivative Instruments (Details 5) (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Jun. 30, 2016 |
Jun. 30, 2015 |
Jun. 30, 2016 |
Jun. 30, 2015 |
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| Derivative Instruments, Gain (Loss) [Line Items] | |||||||||||||
| Interest expense | $ 157 | $ 158 | $ 314 | $ 312 | |||||||||
| Interest Rate Hedging Instruments | |||||||||||||
| Derivative Instruments, Gain (Loss) [Line Items] | |||||||||||||
| Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net | [1],[2] | (6) | 14 | (18) | 8 | ||||||||
| Interest expense | [3] | 0 | 0 | 1 | 1 | ||||||||
| Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Hedging Instruments | |||||||||||||
| Derivative Instruments, Gain (Loss) [Line Items] | |||||||||||||
| Interest expense | [1],[2],[4] | $ (11) | $ (12) | $ (22) | $ (24) | ||||||||
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