Amount of principal due on delinquent mortgage loan within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Paragraph Column H
-Subsection 29

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column H))
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

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- Definition

Current weighted average loan to value ratio of commercial mortgage loan.

+ References

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Original weighted average loan to value ratio of commercial mortgage loan.

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- Definition

Percentage of gross unrealized losses depressed less than twenty percent of cost or amortized cost.

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Variable Interest Entity, Reporting Entity Involvement, Commitments

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- Definition

Number of investment positions in available-for-sale investments in a continuous unrealized loss position for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563

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- Definition

Line items represent financial 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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This item represents disclosure of all significant concentrations of credit risk or market risk arising from the subject financial instrument (as defined), whether from an individual counterparty or groups of counterparties.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13531-108611

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This item represents the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading, available-for-sale, or held-to-maturity, including the unrealized holding gain (loss) of held-to-maturity securities transferred to the trading security category and the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) for available-for-sale securities transferred to trading securities during the period. Additionally, this item would include any gains (losses) realized during the period from the sale of investments accounted for under the cost method of accounting.

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Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
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-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

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- Definition

Amount of investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column G))
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Difference between the carrying amount of assets and liabilities in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the variable interest entity (VIE) and the reporting entity's maximum exposure to loss as a result of its involvement with the VIE, where the reporting entity is not the VIE's primary beneficiary.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=108788376&loc=d3e5728-111685

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Level 4 - Additional Information (Details)	3 Months Ended
Level 4 - Additional Information (Details)	Mar. 31, 2019 USD ($) security	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Concentration Risk [Line Items]
Fair Value, Concentration of Risk, Investments	$ 0		$ 0
AFS securities in an unrealized loss position \| security	743
Percentage of AFS securities depressed less than 20% of cost or amortized cost	100.00%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate	$ 2,085,000,000		2,100,000,000
LTV ratio	52.00%
LTV ratio at origination	63.00%
Variable Interest Entity, Nonconsolidated, Comparison of Carrying Amount of Assets and Liabilities to Maximum Loss Exposure	$ 873,000,000		849,000,000
Held-for-sale
Concentration Risk [Line Items]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate	0		0
Commercial Loan [Member]
Concentration Risk [Line Items]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate	2,085,000,000		2,100,000,000
Commercial Loan [Member] \| Mortgage loans
Concentration Risk [Line Items]
Mortgage loans past due by 90 days or more	0		0
Reclassification out of Accumulated Other Comprehensive Income \| Accumulated Net Unrealized Investment Gain (Loss)
Concentration Risk [Line Items]
Other net realized capital gains (losses)	6,000,000	$ 4,000,000
Variable Interest Entity, Not Primary Beneficiary [Member]
Concentration Risk [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Commitments	$ 469,000,000		$ 474,000,000