Reserve for Life-Contingent Contract Benefits and Contractholder Funds (Details 4) - Variable annuities - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Variable annuity contracts with guarantees
Account balances of separate accounts with guarantees, invested in equity, fixed income and balanced mutual funds	$ 2,920	$ 3,200
Account balances of separate accounts with guarantees, invested in money market mutual funds	364	340
In the event of death
Variable annuity contracts with guarantees
Separate account value	3,280	3,541
Net amount at risk	$ 585	$ 675
Average attained age of contractholders	70 years	69 years
Liability for guarantees related to income benefits
Variable annuity contracts with guarantees
Separate account value	$ 915	$ 967
Net amount at risk	$ 265	$ 281
Weighted average waiting period until guarantee date	0 years	0 years
For cumulative periodic withdrawals
Variable annuity contracts with guarantees
Separate account value	$ 267	$ 294
Net amount at risk	10	10
Guaranteed accumulation benefits
Variable annuity contracts with guarantees
Separate account value	310	371
Net amount at risk	$ 26	$ 31
Weighted average waiting period until guarantee date	3 years	4 years