Investments Purchased with Credit Deterioration (Details) $ in Millions	3 Months Ended
Mar. 31, 2020 USD ($)
Purchased financial assets with credit deterioration [Line Items]
Debt Securities, Available-for-sale, Purchased with Credit Deterioration, Amount at Purchase Price	$ 14
Debt Securities, Available-for-sale, Purchased with Credit Deterioration, Allowance for Credit Loss at Acquisition Date	1
Debt Securities, Available-for-sale, Purchased with Credit Deterioration, Discount (Premium)	1
Debt Securities, Available-for-sale, Purchased with Credit Deterioration, Amount at Par Value	16
Mortgage loans
Purchased financial assets with credit deterioration [Line Items]
Financing Receivable, Purchased with Credit Deterioration, Amount at Purchase Price	0
Financing Receivable, Purchased with Credit Deterioration, Allowance for Credit Loss at Acquisition Date	0
Financing Receivable, Purchased with Credit Deterioration, Discount (Premium)	0
Financing Receivable, Purchased with Credit Deterioration, Amount at Par Value	$ 0

[Line Items] for Purchased financial assets with credit deterioration [Table]

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Amount of allowance for credit loss at acquisition date of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), purchased with credit deterioration.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 10
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922903-210455

+ Details

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- Definition

Amount at par value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), purchased with credit deterioration.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 10
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922903-210455

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- Definition

Amount at purchase price of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), purchased with credit deterioration.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922903-210455

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- Definition

Amount of discount (premium) attributable to other factors on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), purchased with credit deterioration.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 10
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922903-210455

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- Definition

Amount of allowance for credit loss at acquisition date of financing receivable purchased with credit deterioration.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 19
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919265-210447

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- Definition

Amount at par value of financing receivable purchased with credit deterioration.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 19
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919265-210447

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Amount at purchase price of financing receivable purchased with credit deterioration.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 19
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919265-210447

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- Definition

Amount of discount (premium) attributable to other factors on financing receivable purchased with credit deterioration.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 19
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919265-210447

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