Investments - Investments - Net Realized Capital Gains (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Schedule of Investments [Line Items]
Gross gains on sales	$ 26,000,000	$ 46,000,000	$ 91,000,000	$ 184,000,000
Gross losses on sales	(41,000,000)	(16,000,000)	(129,000,000)	(84,000,000)
Net OTTI losses recognized in earnings	(1,000,000)	(1,000,000)	(1,000,000)	(4,000,000)
Transactional foreign currency revaluation	0	0	1,000,000	14,000,000
Net realized capital gains	38,000,000	26,000,000	60,000,000	105,000,000
Other net realized capital gains	39,000,000	27,000,000	61,000,000	109,000,000
Proceeds from Sale of Available-for-sale Securities	4,600,000,000	2,900,000,000	13,100,000,000	11,400,000,000
Net Realized and Unrealized Gain (Loss) on Trading Securities	41		50
Net Unrealized Gain on Securities | Reclassification out of Accumulated Other Comprehensive Income
Schedule of Investments [Line Items]
Other net realized capital gains	(15,000,000)	32,000,000	(59,000,000)	102,000,000
Non-qualifying foreign currency derivatives
Schedule of Investments [Line Items]
Non-qualifying foreign currency derivatives	9,000,000	(1,000,000)	8,000,000	(7,000,000)
Non-qualifying foreign currency derivatives | Other Credit Derivatives
Schedule of Investments [Line Items]
Non-qualifying foreign currency derivatives	8,000,000	(1,000,000)	6,000,000	7,000,000
Other, net
Schedule of Investments [Line Items]
Other, net	7,000,000	(3,000,000)	8,000,000	9,000,000
Equity Securities [Member]
Schedule of Investments [Line Items]
Equity securities	46,000,000	0	88,000,000	0
Net OTTI losses recognized in earnings	0	(1,000,000)	0	(2,000,000)
Foreign Exchange Forward [Member] | Non-qualifying foreign currency derivatives
Schedule of Investments [Line Items]
Non-qualifying foreign currency derivatives	$ 1,000,000	$ 0	$ 2,000,000	$ (14,000,000)