Reserve for Life-Contingent Contract Benefits and Contractholder Funds (Details 4) - Variable annuities - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Variable annuity contracts with guarantees
Account balances of separate accounts with guarantees, invested in equity, fixed income and balanced mutual funds	$ 3,200	$ 3,820
Account balances of separate accounts with guarantees, invested in money market mutual funds	340	467
In the event of death
Variable annuity contracts with guarantees
Separate account value	3,541	4,288
Net amount at risk	$ 675	$ 581
Average attained age of contractholders	69 years	69 years
Liability for guarantees related to income benefits
Variable annuity contracts with guarantees
Separate account value	$ 967	$ 1,142
Net amount at risk	$ 281	$ 238
Weighted average waiting period until guarantee date	0 years	0 years
For cumulative periodic withdrawals
Variable annuity contracts with guarantees
Separate account value	$ 294	$ 382
Net amount at risk	10	8
Guaranteed accumulation benefits
Variable annuity contracts with guarantees
Separate account value	371	480
Net amount at risk	$ 31	$ 24
Weighted average waiting period until guarantee date	4 years	4 years