Investments - Narrative (Details) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($) security	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Investment [Line Items]
Percentage (based on amount of unrealized loss) of available for sale fixed maturities that are in an unrealized loss position and rated investment grade	92.00%
Percentage (based on fair value) of available for sale fixed maturities that are in an unrealized loss position and rated investment grade	96.00%
Other than temporary impairment charges	$ 19	$ 73	$ 116
Average life of ABS	4 years 6 months
Average life of MBS	4 years 6 months
Residential MBS
Investment [Line Items]
Non-credit related portion of other-than-temporary impairment charges taken for securities still owned	$ 140	158
Fixed maturities, Gross Unrealized, Losses	(9)	(6)
Other than temporary impairment charges	6	1	3
Securities with non-credit other-than-temporary impairment charges
Investment [Line Items]
Gross Unrealized, Gains	119	137
Gross Unrealized, Losses	(4)	(4)
Fixed maturities
Investment [Line Items]
Fixed maturities, Gross Unrealized, Losses	$ (603)	(82)
Number of available for sale securities in an unrealized loss position \| security	2,324
Other than temporary impairment charges	$ 26	20	38
Available-for-sale Securities, Gross Realized Gains	22	43	55
Available-for-sale Securities, Gross Realized Losses	(14)	(20)	(10)
Fixed maturities excluding residential MBS
Investment [Line Items]
Other than temporary impairment charges	20	19	35
Other investments
Investment [Line Items]
Other than temporary impairment charges		4
Equity securities
Investment [Line Items]
Other than temporary impairment charges	0	64	93
Available-for-sale Securities, Gross Realized Gains		87	110
Available-for-sale Securities, Gross Realized Losses		(17)	(4)
Equity securities \| Available-for-sale securities
Investment [Line Items]
Other than temporary impairment charges		$ 64	$ 93
Aircraft financing \| Fixed maturities excluding residential MBS
Investment [Line Items]
Other than temporary impairment charges	$ 14

Asset-backed securities average useful life.

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Number of available-for-sale securities in an unrealized loss position.

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Percentage (based on fair value) of available for sale fixed maturities that are in an unrealized loss position and rated investment grade.

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Line items represent reporting concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 12
-Sentence Column A

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
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