Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Millions		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Securities loaned
Cash collateral received as percentage of fair value of securities loaned		102.00%
Cash collateral received for securities loaned percentage foreign		105.00%
Deferred policy acquisition and sales inducement costs
Present value of future profits	$ 3	$ 3	$ 3
Amortization expense of future profits		0	0	$ 0
Equity securities	(308)		(308)
Unrealized Gain (loss)		$ 238
Cumulative effect of change in accounting principle					$ 0
Minimum
Deferred policy acquisition and sales inducement costs
Period for amortization of DAC and DSI for interest-sensitive life, fixed annuities and other investment contracts		15 years
Maximum
Securities loaned
Length of securities lending transaction period		30 days
Deferred policy acquisition and sales inducement costs
Period for amortization of DAC and DSI for interest-sensitive life, fixed annuities and other investment contracts		30 years
Interest-sensitive life insurance | Minimum
Deferred policy acquisition and sales inducement costs
Period for amortization of DAC and DSI for interest-sensitive life, fixed annuities and other investment contracts		10 years
Interest-sensitive life insurance | Maximum
Deferred policy acquisition and sales inducement costs
Period for amortization of DAC and DSI for interest-sensitive life, fixed annuities and other investment contracts		20 years
Fixed annuities | Minimum
Deferred policy acquisition and sales inducement costs
Period for amortization of DAC and DSI for interest-sensitive life, fixed annuities and other investment contracts		5 years
Fixed annuities | Maximum
Deferred policy acquisition and sales inducement costs
Period for amortization of DAC and DSI for interest-sensitive life, fixed annuities and other investment contracts		10 years
Accounting Standards Update 2016-01
Deferred policy acquisition and sales inducement costs
Equity securities	(308)	$ (308)	(308)
EMA limited partnerships | Accounting Standards Update 2016-01
Deferred policy acquisition and sales inducement costs
Investments in and advances to affiliates	95
Retained income
Deferred policy acquisition and sales inducement costs
Cumulative effect of change in accounting principle	314		314	$ 0	$ 0
Limited partnership interests | Retained income | Accounting Standards Update 2016-01
Deferred policy acquisition and sales inducement costs
Cumulative effect of change in accounting principle	$ 76		$ 76