Segment Information (Premiums, Universal Life and Investment-Type Policy Fees and Other Revenues by Major Product Groups) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total premiums, universal life and investment-type product policy fees and other revenues	$ 4,320	$ 4,986	$ 5,363
Annuity products
Segment Reporting Information [Line Items]
Total premiums, universal life and investment-type product policy fees and other revenues	2,729	3,411	3,701
Life insurance (1)
Segment Reporting Information [Line Items]
Total premiums, universal life and investment-type product policy fees and other revenues	1,587	1,552	1,529
Other products
Segment Reporting Information [Line Items]
Total premiums, universal life and investment-type product policy fees and other revenues	$ 4	$ 23	$ 133