Fair Value Measurements - Measured under Certain Conditions (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Fair Value Disclosures [Abstract]
Percentage Of Impaired Commercial Mortgage Loans Of Total Investments		Less than 1%
Realized Investment Losses Commercial Mortgage Loans		$ 7
Percentage Of Impaired Commercial Mortgage Loans And Real Estate Entities Of Total Investments	Less than 1%
Realized Investment Losses Commercial Mortgage Loans And Real Estate Entities	$ 5