Represents the number of securities which had unrealized losses greater than 10% of book value for 12 months or more.

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This item represents the excess of amortized cost basis over fair value of securities that have been in a loss position for twelve months or longer for those securities which are categorized neither as held-to-maturity nor trading securities and which have unrealized losses greater than 10% of book value.

+ References

No definition available.

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- Definition

Represents government agency obligations as a percentage of the aggregate amortized cost of mortgage backed securities.

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- Definition

Non-Income Producing Investments

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- Definition

Number of Outside Managers Managing Investment Portfolio

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No definition available.

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- Definition

Line items represent reporting 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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
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-Sentence Column A

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Interest, dividends, rents, ancillary and other revenues earned but not yet received by the entity on its investments.

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The total amount of cash and securities held by third party trustees pursuant to terms of debt instruments or other agreements as of the date of each statement of financial position presented, which can be used by the trustee only to pay the noncurrent portion of specified obligations.

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Amount of unrealized loss before deducting unrealized gain on investments in available-for-sale equity securities.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

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Investments and Cash - Narrative (Details) $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
Investments and Cash - Narrative (Details) $ in Millions	Jun. 30, 2018 USD ($) Security	Jun. 30, 2018 USD ($) Security	Dec. 31, 2017 USD ($) Security	Jan. 01, 2018 USD ($)	Jun. 30, 2017 USD ($)
Investment [Line Items]
Accrued investment income	$ 93	$ 93	$ 97
Government agency obligations as a percentage of total mortgage backed securities	42.00%	42.00%	39.00%
Number of securities with unrealized losses greater than 10% of book value for 12 months or more \| Security	34	34	28
Total unrealized losses for securities having losses greater than 10% of book value for 12 months or more	$ 37	$ 37	$ 27
Assets held-in-trust	262	$ 262	$ 287
Number of outside managers managing investment portfolio		7
Non-income producing investments	0	$ 0			$ 0
Unrealized Gain (Loss) on Investments	(1)	$ (4)
Investments [Member] \| Internally Managed Portfolio [Member]
Investment [Line Items]
Percentage of installment premiums denominated in currencies other than the U.S. dollar		11.00%	12.00%
AGL Subsidiaries [Member]
Investment [Line Items]
Assets held-in-trust	$ 1,713	$ 1,713	$ 1,677
Accounting Standards Update 2016-01 [Member] \| Retained Earnings [Member]
Investment [Line Items]
New accounting pronouncement or change in accounting principle, effect of change on net income				$ (32)
Redeemable Preferred Stock [Member] \| Other Income [Member] \| Accounting Standards Update 2016-01 [Member] \| Retained Earnings [Member]
Investment [Line Items]
New accounting pronouncement or change in accounting principle, effect of change on net income			$ 1