Fair Value Measurements - Level 4 Changes in Unrealized Gains (Losses) Included in Net Income for Financial Instruments Classified at Fair Value (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ (254)	$ 3
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	65	39
Fair Value, Inputs, Level 3 [Member] | Other Policyholder Funds and Benefits Payable [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	65	39
Fair Value, Inputs, Level 3 [Member] | Guaranteed Minimum Withdrawal Benefit [Member] | Other Policyholder Funds and Benefits Payable [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	65	39
Fair Value, Inputs, Level 3 [Member] | Reinsurance Recoverable Including Reinsurance Premium Paid [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(14)	(8)
Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(240)	11
Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Interest Rate Contract [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(2)	1
Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | US GMWB Hedging Instruments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(25)	(2)
Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | US Macro Hedge Program [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ (213)	$ 12