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Commitments and Contingencies (Estimates of Total Remediation Costs, Weighted Average Risk-Free Rate, Total Remediation Costs - Discounted and Recoverable Portion) (Details) (USD $)
In Millions, unless otherwise specified |
Dec. 31, 2012
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Dec. 31, 2011
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|---|---|---|
| Total remediation costs - undiscounted | $ 202 | $ 227 |
| Weighted average risk-free rate | 5.60% | 5.60% |
| Total remediation costs - discounted | 131 | 152 |
| Recoverable portion | $ 86 | $ 105 |