Fair Value Measurements - Significant Unobservable Inputs Freestanding Derivatives (Details) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Measurement Input, Comparability Adjustment [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Servicing Asset, Measurement Input	0
Significant Unobservable Inputs (Level 3) \| Interest rate swaptions [2] \| Long
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Derivative Assets (Liabilities), at Fair Value, Net	$ 2	$ 1
Significant Unobservable Inputs (Level 3) \| Interest rate swaptions [2] \| Minimum \| Long
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurements, Unobservable Swap_Curve	3.00%	2.00%
Significant Unobservable Inputs (Level 3) \| Interest rate swaptions [2] \| Maximum \| Long
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurements, Unobservable Swap_Curve	3.00%	2.00%
Significant Unobservable Inputs (Level 3) \| Equity Options
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Derivative Assets (Liabilities), at Fair Value, Net	$ 1	$ 1
Significant Unobservable Inputs (Level 3) \| Equity Options \| Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurements, Unobservable Swap_Curve	19.00%	18.00%
Significant Unobservable Inputs (Level 3) \| Equity Options \| Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurements, Unobservable Swap_Curve	26.00%	22.00%

Range of input to the valuation of interest rate swaps that are unobservable due to the swap duration being in excess of the observable swap yield curve.

No definition available.

+ Details

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Namespace Prefix:	hig_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

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Period Type:	duration

- Definition

Value of input used to measure servicing asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

+ Details

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Balance Type:	na
Period Type:	instant

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- Details

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- Details

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- Details

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- Details

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- Details

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