Investments - Investments - Securities Lending, Repurchase Agreements, and Other Collateral Transactions (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Dec. 31, 2020
Securities Lending Transactions:
Required Collateral Held Under Securities Lending, Percentage	100.00%
Securities Loaned	$ 0	$ 0
Reverse Repurchase Agreements, Other Collateral Transactions and Restricted Investments
Securities for Reverse Repurchase Agreements	16	30
Assets Held by Insurance Regulators	$ 2,500	2,600
Domestic
Securities Lending Transactions:
Securities Loaned, Collateral, Percentage Required at Origination	102.00%
Non-domestic
Securities Lending Transactions:
Securities Loaned, Collateral, Percentage Required at Origination	105.00%
US Treasury Securities [Member]
Reverse Repurchase Agreements, Other Collateral Transactions and Restricted Investments
Debt Securities, Available-for-sale, Restricted	$ 9	34
Maximum
Securities Lending Transactions:
Securities Loaned, Term	90 days
Fair Value Measured at Net Asset Value Per Share [Member]
Reverse Repurchase Agreements, Other Collateral Transactions and Restricted Investments
Deposit Assets	$ 61	54
Syndicate Policyholders [Member] \| Debt Securities [Member]
Reverse Repurchase Agreements, Other Collateral Transactions and Restricted Investments
Debt Securities, Available-for-sale, Restricted	673	661
Syndicate Policyholders [Member] \| Short-term investments
Reverse Repurchase Agreements, Other Collateral Transactions and Restricted Investments
Restricted Investments, Current	4	26
Lloyd's of London [Member] \| Debt Securities [Member]
Reverse Repurchase Agreements, Other Collateral Transactions and Restricted Investments
Debt Securities, Available-for-sale, Restricted	$ 171	$ 175

Required Collateral Held Under Securities Lending, Percentage

No definition available.

Name:	hig_RequiredCollateralHeldUnderSecuritiesLendingPercentage
Namespace Prefix:	hig_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Securities Loaned, Collateral, Percentage Required at Origination

+ References

No definition available.

+ Details

Name:	hig_SecuritiesLoanedCollateralPercentageRequiredatOrigination
Namespace Prefix:	hig_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Securities Loaned, Term

+ References

No definition available.

+ Details

Name:	hig_SecuritiesLoanedTerm
Namespace Prefix:	hig_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Carrying amount of cash and investment securities on deposit with state regulatory authorities in connection with capital requirements.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 825
-Section 50
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=75763970&loc=SL75763979-209797

+ Details

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

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729

+ Details

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

- Definition

The carrying amount of the asset transferred to a third party to serve as a deposit, which typically serves as security against failure by the transferor to perform under terms of an agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.8,17)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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

- Definition

This element represents the current portion of investments which are not defined as or included in marketable (debt, equity, or other) securities that are pledged or subject to withdrawal restrictions.

+ References

No definition available.

+ Details

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

- Definition

The carrying value of securities purchased to be resold in reverse repurchase transactions as of the balance sheet date.

+ References

No definition available.

+ Details

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

- Definition

Amount, after the effects of master netting arrangements, of securities loaned to entities in exchange for collateral. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

+ Details

Name:	us-gaap_SecuritiesLoaned
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Details

Name:	us-gaap_InvestmentTypeAxis=hig_DomesticMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=hig_NondomesticMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	hig_RestrictionAxis=hig_SyndicatePolicyholdersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_DebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_ShortTermInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	hig_RestrictionAxis=hig_LloydsofLondonMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: