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Summary of Significant Accounting Policies (Details) (USD $)
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3 Months Ended | 9 Months Ended | 3 Months Ended | ||||||
|---|---|---|---|---|---|---|---|---|---|
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Sep. 30, 2012
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Sep. 30, 2011
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Sep. 30, 2012
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Sep. 30, 2011
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Jan. 01, 2009
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Sep. 30, 2012
United Kingdom
Change in Corporate Income Tax Rate [Member]
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Sep. 30, 2011
United Kingdom
Change in Corporate Income Tax Rate [Member]
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Jul. 17, 2012
United Kingdom
Change in Corporate Income Tax Rate [Member]
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Jul. 19, 2011
United Kingdom
Change in Corporate Income Tax Rate [Member]
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| Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items] | |||||||||
| Value assigned to equity interest to the acquired reporting entity | $ 29,100,000,000 | ||||||||
| Reduction in Statutory Corporate Income Tax Rate | 2.00% | 2.00% | |||||||
| Statutory Corporate Income Tax Rate | 23.00% | 25.00% | |||||||
| Income tax provision (benefit) | $ 191,000,000 | $ (523,000,000) | $ (735,000,000) | $ (1,329,000,000) | $ 781,000,000 | $ 774,000,000 | |||