Investments Investments - Allowance for Credit Losses Rollforward (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2020
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Debt Securities, Available-for-sale, Allowance for Credit Loss, Beginning Balance	$ 173
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not Previously Recorded	15	$ 109
Debt Securities, Available-for-sale, Allowance for Credit Loss, Purchased with Credit Deterioration, Increase	0	61
Debt Securities, Available-for-sale, Allowance for Credit Loss, Securities Sold	(15)	(17)
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not to Sell before Recovery, Credit Loss, Previously Recorded, Expense (Reversal)	(33)	(30)
Corporate
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Debt Securities, Available-for-sale, Allowance for Credit Loss, Beginning Balance	31
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not Previously Recorded	1	32
Debt Securities, Available-for-sale, Allowance for Credit Loss, Purchased with Credit Deterioration, Increase	0	0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Securities Sold	(2)	(2)
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not to Sell before Recovery, Credit Loss, Previously Recorded, Expense (Reversal)	0	0
CLO
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Debt Securities, Available-for-sale, Allowance for Credit Loss, Beginning Balance	1	0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not Previously Recorded	0	1
Debt Securities, Available-for-sale, Allowance for Credit Loss, Purchased with Credit Deterioration, Increase	0	0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Securities Sold	0	0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not to Sell before Recovery, Credit Loss, Previously Recorded, Expense (Reversal)	0	0
ABS
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Debt Securities, Available-for-sale, Allowance for Credit Loss, Beginning Balance	2
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not Previously Recorded	0	5
Debt Securities, Available-for-sale, Allowance for Credit Loss, Purchased with Credit Deterioration, Increase	0	0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Securities Sold	0	0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not to Sell before Recovery, Credit Loss, Previously Recorded, Expense (Reversal)	1	(2)
CMBS
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Debt Securities, Available-for-sale, Allowance for Credit Loss, Beginning Balance	10
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not Previously Recorded	12	21
Debt Securities, Available-for-sale, Allowance for Credit Loss, Purchased with Credit Deterioration, Increase	0	0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Securities Sold	(1)	(1)
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not to Sell before Recovery, Credit Loss, Previously Recorded, Expense (Reversal)	(2)	(1)
RMBS
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Debt Securities, Available-for-sale, Allowance for Credit Loss, Beginning Balance	129
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not Previously Recorded	2	50
Debt Securities, Available-for-sale, Allowance for Credit Loss, Purchased with Credit Deterioration, Increase	0	61
Debt Securities, Available-for-sale, Allowance for Credit Loss, Securities Sold	(12)	(14)
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not to Sell before Recovery, Credit Loss, Previously Recorded, Expense (Reversal)	(32)	(27)
Related Party
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Debt Securities, Available-for-sale, Allowance for Credit Loss, Beginning Balance	2	0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not Previously Recorded	1	2
Debt Securities, Available-for-sale, Allowance for Credit Loss, Purchased with Credit Deterioration, Increase	0	0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Securities Sold	(1)	(1)
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not to Sell before Recovery, Credit Loss, Previously Recorded, Expense (Reversal)	0	1
Related Party \| CLO
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Debt Securities, Available-for-sale, Allowance for Credit Loss, Beginning Balance	2
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not Previously Recorded	1	2
Debt Securities, Available-for-sale, Allowance for Credit Loss, Purchased with Credit Deterioration, Increase	0	0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Securities Sold	(1)	(1)
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not to Sell before Recovery, Credit Loss, Previously Recorded, Expense (Reversal)	0	1
Investments including related party
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Debt Securities, Available-for-sale, Allowance for Credit Loss, Beginning Balance	175
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not Previously Recorded	16	111
Debt Securities, Available-for-sale, Allowance for Credit Loss, Purchased with Credit Deterioration, Increase	0	61
Debt Securities, Available-for-sale, Allowance for Credit Loss, Securities Sold	(16)	(18)
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not to Sell before Recovery, Credit Loss, Previously Recorded, Expense (Reversal)	$ (33)	$ (29)

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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121582814&loc=SL82922900-210455

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 9
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=121582814&loc=SL82922900-210455

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454

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- Definition

Amount of expense for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), for which no credit loss was previously recorded.

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- Definition

Amount of expense (reversal of expense) for allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), not intended to be sold and not more likely than not will be required to sell before recovery of amortized cost basis, with previously recorded allowance.

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- Definition

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

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of decrease in allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) from sale.

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