Derivatives - Narrative (Details)	3 Months Ended
	Mar. 31, 2018 USD ($) swap	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Carrying value of collateral received to support purchased call options	$ 356,000,000		$ 389,000,000
Cash Flow Hedges | Designated as Hedging Instrument | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Number of interest rate swaps designated and qualifying as a cash flow hedges | swap	11
Notional amount of derivative instrument outstanding	$ 1,680,000,000		1,580,000,000
Gain (loss) reclassified from AOCI into net investment income	1,000,000	$ 2,000,000
Gain (loss) on cash flow hedge ineffectiveness recorded in Net Earnings	0	$ 0
Collateral receivable supporting interest rate swaps	107,000,000		70,000,000
Other assets | Cash Flow Hedges | Designated as Hedging Instrument | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Net derivatives, at fair value	0
Other assets | Maximum | Cash Flow Hedges | Designated as Hedging Instrument | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Net derivatives, at fair value			1,000,000
Other liabilities | Cash Flow Hedges | Designated as Hedging Instrument | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Net derivatives, at fair value	(61,000,000)		$ (31,000,000)
New interest rate swaps entered into during the period | Cash Flow Hedges | Designated as Hedging Instrument | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instrument outstanding	$ 130,000,000
Number of interest rate swaps entered into during the period | swap	1