Investments (Net Investment Gains Losses - Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Non-investment portfolio gains (losses)	$ (18,000,000)	$ 20,000,000	$ (14,000,000)	$ 26,000,000
Gains (losses) from foreign currency transactions	$ 53,000,000	(118,000,000)	$ (29,000,000)	(225,000,000)
MetLife Assurance Limited
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Non-investment portfolio gains (losses)		$ 0		$ 633,000,000