Investments - Carrying value of non-impaired mortgage loans summarized by debt service coverage ratio distribution (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
Total	$ 4,681	$ 4,670
Mortgage loans, non-impaired
Financing Receivable, Impaired [Line Items]
Fixed rate mortgage loans	4,545	4,534
Variable rate mortgage loans	132	132
Total	4,677	4,666
Below 1.0 \| Mortgage loans, non-impaired
Financing Receivable, Impaired [Line Items]
Fixed rate mortgage loans	22	6
Variable rate mortgage loans	31	31
Total	53	37
1.0 - 1.25 \| Mortgage loans, non-impaired
Financing Receivable, Impaired [Line Items]
Fixed rate mortgage loans	256	273
Variable rate mortgage loans	0	0
Total	256	273
1.26 - 1.50 \| Mortgage loans, non-impaired
Financing Receivable, Impaired [Line Items]
Fixed rate mortgage loans	1,157	1,192
Variable rate mortgage loans	0	0
Total	1,157	1,192
Above 1.50 \| Mortgage loans, non-impaired
Financing Receivable, Impaired [Line Items]
Fixed rate mortgage loans	3,110	3,063
Variable rate mortgage loans	101	101
Total	$ 3,211	$ 3,164

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- Definition

Amount of loan with fixed rate of interest.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

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- Definition

Amount of loan with variable or adjustable rate of interest.

+ References

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- Definition

The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(c))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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