Investments - Other-than-temporary impairment losses by asset type (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment (“OTTI”) losses	$ (146)	$ (313)	$ (452)
Included in OCI	(4)	10	36
Net OTTI losses recognized in earnings	(150)	(303)	(416)
Fixed income securities
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment (“OTTI”) losses	(22)	(54)	(111)
Included in OCI	(4)	10	36
Net OTTI losses recognized in earnings	(26)	(44)	(75)
Municipal
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment (“OTTI”) losses	(1)	0	(17)
Included in OCI	(3)	0	4
Net OTTI losses recognized in earnings	(4)	0	(13)
Corporate
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment (“OTTI”) losses	(9)	(33)	(61)
Included in OCI	3	9	11
Net OTTI losses recognized in earnings	(6)	(24)	(50)
ABS
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment (“OTTI”) losses	(1)	(6)	(33)
Included in OCI	(2)	0	22
Net OTTI losses recognized in earnings	(3)	(6)	(11)
RMBS
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment (“OTTI”) losses	(2)	0	1
Included in OCI	(3)	(1)	(1)
Net OTTI losses recognized in earnings	(5)	(1)	0
CMBS
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment (“OTTI”) losses	(9)	(15)	(1)
Included in OCI	1	2	0
Net OTTI losses recognized in earnings	(8)	(13)	(1)
Equity securities
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment (“OTTI”) losses	(86)	(194)	(279)
Included in OCI	0	0	0
Net OTTI losses recognized in earnings	(86)	(194)	(279)
Mortgage loans
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment (“OTTI”) losses	(1)	0	4
Included in OCI	0	0	0
Net OTTI losses recognized in earnings	(1)	0	4
Limited partnership interests
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment (“OTTI”) losses	(32)	(56)	(51)
Included in OCI	0	0	0
Net OTTI losses recognized in earnings	(32)	(56)	(51)
Other
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment (“OTTI”) losses	(5)	(9)	(15)
Included in OCI	0	0	0
Net OTTI losses recognized in earnings	$ (5)	$ (9)	$ (15)

No definition available.

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- Definition

The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 35
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=82895926&loc=d3e25351-111560

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- Definition

Amount before tax of other than temporary impairment loss (OTTI) on investments in available-for-sale and held-to-maturity debt securities, recognized in other comprehensive loss and attributable to parent entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e637-108580

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-Name Accounting Standards Codification
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- Definition

The amount of other than temporary impairment (OTTI) losses on equity securities, OTTI related to credit losses on debt securities, and OTTI losses on debt securities when the entity intends to sell the securities or it is more likely than not that the entity will be required to sell the securities before recovery of its amortized cost basis. Additionally, this item includes OTTI losses recognized during the period on investments accounted for under the cost method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=82897076&loc=SL6284393-111563

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