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Fair Value of Financial Instruments (Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis) (Details) (USD $)
In Millions, unless otherwise specified |
Mar. 31, 2014
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Dec. 31, 2013
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||||||||
| Financial investments, at fair value | $ 197 | [1] | $ 189 | [1] | ||||
| Default fund investments | 2,211 | [2] | 1,867 | [2] | ||||
| Total | 2,408 | 2,056 | ||||||
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Level 1 [Member]
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||||||||
| Financial investments, at fair value | 192 | [1] | 189 | [1] | ||||
| Default fund investments | 710 | [2] | 774 | [2] | ||||
| Total | 902 | 963 | ||||||
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Level 2 [Member]
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||||||||
| Financial investments, at fair value | 5 | [1] | ||||||
| Default fund investments | 1,501 | [2] | 1,093 | [2] | ||||
| Total | $ 1,506 | $ 1,093 | ||||||
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