Investments - Investments - Commercial Mortgage Loans Credit Quality (Details)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Financing Receivable, Recorded Investment [Line Items]
Carrying Value	$ 3,355,000,000	$ 3,175,000,000
Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Carrying Value	$ 3,355,000,000	$ 3,175,000,000
Avg. Debt-Service Coverage Ratio	2.68	2.69
Commercial Loan [Member] \| Greater than 80%
Financing Receivable, Recorded Investment [Line Items]
Carrying Value	$ 0	$ 18,000,000
Avg. Debt-Service Coverage Ratio	0.00	1.27
Commercial Loan [Member] \| 65% - 80%
Financing Receivable, Recorded Investment [Line Items]
Carrying Value	$ 361,000,000	$ 265,000,000
Avg. Debt-Service Coverage Ratio	1.63	1.95
Commercial Loan [Member] \| Less than 65%
Financing Receivable, Recorded Investment [Line Items]
Carrying Value	$ 2,994,000,000	$ 2,892,000,000
Avg. Debt-Service Coverage Ratio	2.76	2.76
Mortgage loans \| Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage Loans on Real Estate, Principal Amount of Delinquent Loans	$ 0

Average debt service coverage ratio.

No definition available.

Name:	hig_AverageDebtServiceCoverageRatio
Namespace Prefix:	hig_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

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

- Definition

The carrying amount of the outstanding balance due under the mortgage loan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
-Subparagraph (SX 210.5-04.(c) Schedule IV)
-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

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

+ Details

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

- Definition

Amount of principal due on loans that have been delinquent, which may exclude loans having interest delinquent for three months or less, as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
-Subparagraph (SX 210.5-04.(c) Schedule IV)
-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29.10(a))
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

+ Details

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

- Details

Name:	us-gaap_MortgageLoansOnRealEstateLoanTypeAxis=us-gaap_CommercialLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanToValueAxis=us-gaap_Ltv80To100PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanToValueAxis=hig_LTVBetween65to80PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanToValueAxis=hig_LTVLessthan65PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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