Level 4~Investments - Net Realized Capital Gains (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Schedule of Investments [Line Items]
Proceeds from Sale of Available-for-sale Securities	$ 4,300	$ 4,300
Gross gains on sales	19	61
Gross losses on sales	(57)	(46)
Net OTTI losses recognized in earnings	0	(1)
Transactional foreign currency revaluation	1	6
Total net realized capital gains (losses)	(30)	24
Other investments
Schedule of Investments [Line Items]
Other, net	(6)	11
Non-qualifying
Schedule of Investments [Line Items]
Non-qualifying foreign currency derivatives	(13)	0
Foreign Currency Derivatives | Non-qualifying
Schedule of Investments [Line Items]
Non-qualifying foreign currency derivatives	(3)	(7)
Equity Securities [Member]
Schedule of Investments [Line Items]
Realized Gain (Loss) on Marketable Securities and Cost Method Investments, Excluding Other than Temporary Impairments, and Other Investments	16	0
Net OTTI losses recognized in earnings	0	0
Other Credit Derivatives [Member] | Non-qualifying
Schedule of Investments [Line Items]
Non-qualifying foreign currency derivatives	$ (10)	$ 7