Derivative Financial Instruments and Off-balance sheet Financial Instruments - Foreign currency contracts in cash flow hedging and other (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss)
Cash flow hedge gain (loss) to be reclassified from AOCI during the next twelve months	$ 2,000,000
Hedge ineffectiveness in realized gains	0	$ 0	$ 0
(Loss) gain recognized in OCI on derivatives during the period	(2,000,000)	(1,000,000)	10,000,000
Gain recognized in OCI on derivatives during the term of the hedging relationship	2,000,000	5,000,000	10,000,000
Total gain (loss) recognized in net income on derivatives	33,000,000	33,000,000	25,000,000
Net investment income | Reclassification out of Accumulated Other Comprehensive Income | Cash flow hedges
Derivative Instruments, Gain (Loss)
Investment income, net	1,000,000	1,000,000	(1,000,000)
Realized capital gains and losses
Derivative Instruments, Gain (Loss)
Total gain (loss) recognized in net income on derivatives	(16,000,000)	5,000,000	10,000,000
Realized capital gains and losses | Reclassification out of Accumulated Other Comprehensive Income | Cash flow hedges
Derivative Instruments, Gain (Loss)
Investment income, net	0	3,000,000	3,000,000
Contract benefits
Derivative Instruments, Gain (Loss)
Total gain (loss) recognized in net income on derivatives	9,000,000	9,000,000	(7,000,000)
Interest credited to contractholder funds
Derivative Instruments, Gain (Loss)
Total gain (loss) recognized in net income on derivatives	40,000,000	19,000,000	22,000,000
Equity and index contracts
Derivative Instruments, Gain (Loss)
Derivatives not designated as accounting hedging instruments, total gain (loss) recognized in net income on derivatives	41,000,000	14,000,000	(9,000,000)
Equity and index contracts | Realized capital gains and losses
Derivative Instruments, Gain (Loss)
Derivatives not designated as accounting hedging instruments, total gain (loss) recognized in net income on derivatives	(4,000,000)	(4,000,000)	0
Equity and index contracts | Contract benefits
Derivative Instruments, Gain (Loss)
Derivatives not designated as accounting hedging instruments, total gain (loss) recognized in net income on derivatives	0	0	0
Equity and index contracts | Interest credited to contractholder funds
Derivative Instruments, Gain (Loss)
Derivatives not designated as accounting hedging instruments, total gain (loss) recognized in net income on derivatives	45,000,000	18,000,000	(9,000,000)
Embedded derivative financial instruments
Derivative Instruments, Gain (Loss)
Derivatives not designated as accounting hedging instruments, total gain (loss) recognized in net income on derivatives	4,000,000	10,000,000	24,000,000
Embedded derivative financial instruments | Realized capital gains and losses
Derivative Instruments, Gain (Loss)
Derivatives not designated as accounting hedging instruments, total gain (loss) recognized in net income on derivatives	0	0	0
Embedded derivative financial instruments | Contract benefits
Derivative Instruments, Gain (Loss)
Derivatives not designated as accounting hedging instruments, total gain (loss) recognized in net income on derivatives	9,000,000	9,000,000	(7,000,000)
Embedded derivative financial instruments | Interest credited to contractholder funds
Derivative Instruments, Gain (Loss)
Derivatives not designated as accounting hedging instruments, total gain (loss) recognized in net income on derivatives	(5,000,000)	1,000,000	31,000,000
Foreign currency contracts
Derivative Instruments, Gain (Loss)
Derivatives not designated as accounting hedging instruments, total gain (loss) recognized in net income on derivatives	(14,000,000)	6,000,000	6,000,000
Foreign currency contracts | Realized capital gains and losses
Derivative Instruments, Gain (Loss)
Derivatives not designated as accounting hedging instruments, total gain (loss) recognized in net income on derivatives	(14,000,000)	6,000,000	6,000,000
Foreign currency contracts | Contract benefits
Derivative Instruments, Gain (Loss)
Derivatives not designated as accounting hedging instruments, total gain (loss) recognized in net income on derivatives	0	0	0
Foreign currency contracts | Interest credited to contractholder funds
Derivative Instruments, Gain (Loss)
Derivatives not designated as accounting hedging instruments, total gain (loss) recognized in net income on derivatives	0	0	0
Credit default swaps
Derivative Instruments, Gain (Loss)
Derivatives not designated as accounting hedging instruments, total gain (loss) recognized in net income on derivatives	2,000,000	3,000,000	4,000,000
Credit default swaps | Realized capital gains and losses
Derivative Instruments, Gain (Loss)
Derivatives not designated as accounting hedging instruments, total gain (loss) recognized in net income on derivatives	2,000,000	3,000,000	4,000,000
Credit default swaps | Contract benefits
Derivative Instruments, Gain (Loss)
Derivatives not designated as accounting hedging instruments, total gain (loss) recognized in net income on derivatives	0	0	0
Credit default swaps | Interest credited to contractholder funds
Derivative Instruments, Gain (Loss)
Derivatives not designated as accounting hedging instruments, total gain (loss) recognized in net income on derivatives	$ 0	$ 0	$ 0