Investments - Investments - Net Realized Capital Gains (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Schedule of Investments [Line Items]
Gross gains on sales	$ 46,000,000	$ 77,000,000	$ 65,000,000	$ 138,000,000
Gross losses on sales	(31,000,000)	(22,000,000)	(88,000,000)	(68,000,000)
Net OTTI losses recognized in earnings	0	(2,000,000)	0	(3,000,000)
Transactional foreign currency revaluation	0	8,000,000	1,000,000	14,000,000
Net realized capital gains	52,000,000	55,000,000	22,000,000	79,000,000
Other net realized capital gains	52,000,000	57,000,000	22,000,000	82,000,000
Proceeds from Sale of Available-for-sale Securities	4,200,000,000	4,200,000,000	8,500,000,000	8,500,000,000
Net Realized and Unrealized Gain (Loss) on Trading Securities	17		11
Other, net
Schedule of Investments [Line Items]
Other, net	7,000,000	1,000,000	1,000,000	12,000,000
Net Unrealized Gain on Securities | Reclassification out of Accumulated Other Comprehensive Income
Schedule of Investments [Line Items]
Other net realized capital gains	(6,000,000)	56,000,000	(44,000,000)	71,000,000
Non-qualifying foreign currency derivatives
Schedule of Investments [Line Items]
Non-qualifying foreign currency derivatives	12,000,000	(6,000,000)	(1,000,000)	(6,000,000)
Non-qualifying foreign currency derivatives | Other Credit Derivatives
Schedule of Investments [Line Items]
Non-qualifying foreign currency derivatives	8,000,000	1,000,000	(2,000,000)	8,000,000
Equity Securities [Member]
Schedule of Investments [Line Items]
Equity securities	26,000,000	0	42,000,000	0
Net OTTI losses recognized in earnings	$ 0	$ (1,000,000)	$ 0	$ (1,000,000)