Derivative Instruments - Derivatives - Credit Risk Assumed through Credit Derivatives (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
Jun. 30, 2019	Dec. 31, 2018
Credit Derivatives [Line Items]
Notional Amount	$ 12,361	$ 12,291
Fair Value	(60)	(61)
Credit Default Swap, Selling Protection [Member]
Credit Derivatives [Line Items]
Notional Amount	532	1,123
Credit derivatives
Credit Derivatives [Line Items]
Fair Value	5	(3)
Offsetting Notional Amount	18	21
Offsetting Fair Value	6	6
Credit derivatives \| Single name credit default swaps \| A Minus \| Investment grade risk exposure
Credit Derivatives [Line Items]
Notional Amount	165
Fair Value	$ 4
Weighted Average Years to Maturity	5 years
Offsetting Notional Amount	$ 0
Offsetting Fair Value	0
Credit derivatives \| Single name credit default swaps \| A \| Investment grade risk exposure
Credit Derivatives [Line Items]
Notional Amount		169
Fair Value		$ 2
Weighted Average Years to Maturity		4 years
Offsetting Notional Amount		$ 0
Offsetting Fair Value		0
Credit derivatives \| Basket credit default swaps \| A Minus \| Investment grade risk exposure
Credit Derivatives [Line Items]
Notional Amount		11
Fair Value		$ 0
Weighted Average Years to Maturity		5 years
Offsetting Notional Amount		$ 2
Offsetting Fair Value		0
Credit derivatives \| Basket credit default swaps \| BBB Plus \| Investment grade risk exposure
Credit Derivatives [Line Items]
Notional Amount	350	799
Fair Value	$ 7	$ (1)
Weighted Average Years to Maturity	5 years	6 years
Offsetting Notional Amount	$ 0	$ 0
Offsetting Fair Value	0	0
Credit derivatives \| Basket credit default swaps \| B Plus \| Below investment grade risk exposure
Credit Derivatives [Line Items]
Notional Amount		125
Fair Value		$ 2
Weighted Average Years to Maturity		5 years
Offsetting Notional Amount		$ 0
Offsetting Fair Value		0
Credit derivatives \| Basket credit default swaps \| A \| Investment grade risk exposure
Credit Derivatives [Line Items]
Notional Amount	1
Fair Value	$ 0
Average Term of Credit Risk Derivatives Less than 1 Year	Less than 1 year
Offsetting Notional Amount	$ 1
Offsetting Fair Value	0
Credit derivatives \| Basket credit default swaps \| CCC \| Below investment grade risk exposure
Credit Derivatives [Line Items]
Notional Amount	16	19
Fair Value	$ (6)	$ (6)
Average Term of Credit Risk Derivatives Less than 1 Year	Less than 1 year	Less than 1 year
Offsetting Notional Amount	$ 17	$ 19
Offsetting Fair Value	$ 6	$ 6

Average Term of Credit Risk Derivatives Less than 1 Year

No definition available.

Name:	hig_AverageTermofCreditRiskDerivativesLessthan1Year
Namespace Prefix:	hig_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Derivative, Nominal Value, Amount Offset Against Collateral, Net

+ References

No definition available.

+ Details

Name:	hig_DerivativeNominalValueAmountOffsetAgainstCollateralNet
Namespace Prefix:	hig_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Average period covered by credit risk derivative contracts, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4K
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5708775-113959

+ Details

Name:	us-gaap_AverageTermOfCreditRiskDerivatives1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- 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.

+ References

No definition available.

+ Details

Name:	us-gaap_CreditDerivativesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The net amount as of the balance sheet date of the fair value of derivative assets and derivative liabilities that in accordance with the entity's accounting policy were offset against collateral under a master netting arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=d3e41678-113959

+ Details

Name:	us-gaap_DerivativeFairValueAmountOffsetAgainstCollateralNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611

+ Details

Name:	us-gaap_DerivativeFairValueOfDerivativeNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_CreditDerivativesByContractTypeAxis=us-gaap_CreditDefaultSwapSellingProtectionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_CreditRiskContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditDerivativesByContractTypeAxis=hig_SingleNameCreditDefaultSwapsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CreditRatingStandardPoorsAxis=srt_StandardPoorsAMinusRatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ExternalCreditRatingByGroupingAxis=us-gaap_ExternalCreditRatingInvestmentGradeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CreditRatingStandardPoorsAxis=srt_StandardPoorsARatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditDerivativesByContractTypeAxis=hig_BasketCreditDefaultSwapsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CreditRatingStandardPoorsAxis=srt_StandardPoorsBBBPlusRatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CreditRatingStandardPoorsAxis=srt_StandardPoorsBPlusRatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ExternalCreditRatingByGroupingAxis=us-gaap_ExternalCreditRatingNonInvestmentGradeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CreditRatingStandardPoorsAxis=srt_StandardPoorsCCCRatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: