Variable Annuity and Insurance Guarantees (Liability Rollforward) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 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		1	1
Paid claims		(1)	(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	[1]	463	1,017
Incurred claims	[1]	(261)	(380)
Balance, at the end of the period	[1]	202	637
GMAB [Member]
Changes in Additional Liabilities for Variable Annuity and Insurance Guarantees
Balance, at the beginning of the period	[1]	(80)	(24)
Incurred claims	[1]	4	(29)
Balance, at the end of the period	[1]	(76)	(53)
UL [Member]
Changes in Additional Liabilities for Variable Annuity and Insurance Guarantees
Balance, at the beginning of the period		489	434
Incurred claims		26	23
Paid claims		(7)	(8)
Balance, at the end of the period		$ 508	$ 449

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