Fair Value Measurements - Measured under Certain Conditions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012
Fair Value Disclosures [Abstract]
Percentage Of Impaired Commercial Mortgage Loans Of Total Investments	less than 1
Realized Investment Losses Commercial Mortgage Loans	$ 2

The percentage of total investments represented by impaired commercial mortgage loans.

No definition available.

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