Variable Annuity and Insurance Guarantees (Liability Rollforward) (Details) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017
GMDB and GGU [Member]
Changes in Additional Liabilities for Variable Annuity and Insurance Guarantees
Balance, at the beginning of the period		$ 17	$ 16
Incurred claims		3	1
Paid claims		(3)	(1)
Balance, at the end of the period		17	16
GMIB [Member]
Changes in Additional Liabilities for Variable Annuity and Insurance Guarantees
Balance, at the beginning of the period		6	8
Paid claims		0	(1)
Balance, at the end of the period		6	7
GMWB [Member]
Changes in Additional Liabilities for Variable Annuity and Insurance Guarantees
Balance, at the beginning of the period		463	1,017
Incurred claims	[1]	(335)	(278)
Balance, at the end of the period		128	739
GMAB [Member]
Changes in Additional Liabilities for Variable Annuity and Insurance Guarantees
Balance, at the beginning of the period		(80)	(24)
Incurred claims	[1]	5	(33)
Balance, at the end of the period		(75)	(57)
UL [Member]
Changes in Additional Liabilities for Variable Annuity and Insurance Guarantees
Balance, at the beginning of the period		489	434
Incurred claims		53	52
Paid claims		(13)	(16)
Balance, at the end of the period		$ 529	$ 470

[1] The incurred claims for GMWB and GMAB include the change in the fair value of the liabilities (contra liabilities) less paid claims.