Subsequent Events	9 Months Ended
Sep. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Effective October 2017, the Company changed from four to seven reportable segments: Allstate Protection, Discontinued Lines and Coverages, Service Businesses, Allstate Life, Allstate Benefits, Allstate Annuities and Corporate and Other. These segments align with the Company’s key product and service offerings, including the acquisition of SquareTrade and the strategic focus and expansion of Arity and other emerging businesses. These new segments reflect the manner in which the Company’s chief operating decision maker will review performance and make decisions about the allocation of resources. Goodwill Upon adoption of the new segments in the fourth quarter 2017, the Company is required to evaluate goodwill, including the allocation of goodwill to any new reporting units on a relative fair value basis. The Company allocated the $1.09 billion of goodwill recorded in conjunction with the acquisition of SquareTrade to the Service Businesses reporting unit along with an immaterial amount of goodwill from the Allstate Protection segment related to other businesses included in this segment. The Allstate Financial segment had goodwill that will be reallocated between the new Allstate Life, Allstate Benefits, and Allstate Annuities segments. While substantially all of Allstate Financial goodwill related to the acquisition of Allstate Benefits, the Company is required to allocate a portion of the goodwill to the Allstate Life and Allstate Annuities segments. The estimated allocation is $170 million to Allstate Life, $100 million to Allstate Benefits and $125 million to Allstate Annuities. The reallocation was computed using fair values for the goodwill reporting units determined using discounted cash flow (“DCF”) calculations and market to book multiples derived from a peer company analysis. The DCF analysis utilizes long term assumptions for revenues, investment income, benefits, claims, other operating expenses and income taxes to produce projections of both income and cash flows available for dividends that are present valued using weighted average cost of capital. Market to book multiples represent the mean market to book multiple for selected peer companies with operations similar to the Company’s goodwill reporting units to which the multiple is applied. The outputs from these methods are weighted based on the nature of the business and the relative amount of market observable assumptions supporting the estimates. The computed values were then weighted to reflect the fair value estimate based on the specific attributes of each goodwill reporting unit. A goodwill impairment assessment is required to be completed in conjunction with the segment changes. The Company estimates it will recognize an impairment of approximately $125 million in the fourth quarter of 2017 related to the goodwill allocated to the Allstate Annuities reporting unit reflecting a market-based valuation. Reserve for life-contingent contract benefits Prior to fourth quarter 2017, the Company evaluated the adequacy of reserves and recoverability of DAC for traditional life insurance products and immediate annuities with life contingencies on an aggregate basis. The Company also evaluated these policies on an aggregate basis for circumstances where projected profits would be recognized in early years followed by projected losses in later years. As of September 30, 2017, both traditional life insurance and immediate annuities with life contingencies had projected profit as measured using actual and expected investment holdings and returns; however, the aggregate sufficiency substantially related to traditional life insurance with a marginal sufficiency related to immediate annuities with life contingencies. In conjunction with the segment change in fourth quarter 2017, the Company will review traditional life insurance products and immediate annuities with life contingencies separately. The Company records an adjustment to the reserve for life-contingent contract benefits that represents the amount by which the reserve balance would increase if the net unrealized gains in the applicable product investment portfolios were realized and reinvested at current lower interest rates, resulting in a premium deficiency. The offset to this liability is recorded as a reduction of the unrealized net capital gains included in accumulated other comprehensive income. As of September 30, 2017, no adjustment was recorded. In conjunction with the segment change in fourth quarter 2017, the Company will evaluate the need for a reserve adjustment separately for traditional life insurance and immediate annuities with life contingencies. The estimated impact, using values as of September 30, 2017, is approximately a $550 million increase to the reserve for life-contingent contract benefits, and a $350 million decrease to unrealized net capital gains, after-tax, included in shareholders’ equity.

Subsequent Events

Effective October 2017, the Company changed from four to seven reportable segments: Allstate Protection, Discontinued Lines and Coverages, Service Businesses, Allstate Life, Allstate Benefits, Allstate Annuities and Corporate and Other. These segments align with the Company’s key product and service offerings, including the acquisition of SquareTrade and the strategic focus and expansion of Arity and other emerging businesses. These new segments reflect the manner in which the Company’s chief operating decision maker will review performance and make decisions about the allocation of resources.

Goodwill

Upon adoption of the new segments in the fourth quarter 2017, the Company is required to evaluate goodwill, including the allocation of goodwill to any new reporting units on a relative fair value basis. The Company allocated the $1.09 billion of goodwill recorded in conjunction with the acquisition of SquareTrade to the Service Businesses reporting unit along with an immaterial amount of goodwill from the Allstate Protection segment related to other businesses included in this segment. The Allstate Financial segment had goodwill that will be reallocated between the new Allstate Life, Allstate Benefits, and Allstate Annuities segments. While substantially all of Allstate Financial goodwill related to the acquisition of Allstate Benefits, the Company is required to allocate a portion of the goodwill to the Allstate Life and Allstate Annuities segments. The estimated allocation is $170 million to Allstate Life, $100 million to Allstate Benefits and $125 million to Allstate Annuities.

The reallocation was computed using fair values for the goodwill reporting units determined using discounted cash flow (“DCF”) calculations and market to book multiples derived from a peer company analysis. The DCF analysis utilizes long term assumptions for revenues, investment income, benefits, claims, other operating expenses and income taxes to produce projections of both income and cash flows available for dividends that are present valued using weighted average cost of capital. Market to book multiples represent the mean market to book multiple for selected peer companies with operations similar to the Company’s goodwill reporting units to which the multiple is applied. The outputs from these methods are weighted based on the nature of the business and the relative amount of market observable assumptions supporting the estimates. The computed values were then weighted to reflect the fair value estimate based on the specific attributes of each goodwill reporting unit.

A goodwill impairment assessment is required to be completed in conjunction with the segment changes. The Company estimates it will recognize an impairment of approximately $125 million in the fourth quarter of 2017 related to the goodwill allocated to the Allstate Annuities reporting unit reflecting a market-based valuation.

Reserve for life-contingent contract benefits

Prior to fourth quarter 2017, the Company evaluated the adequacy of reserves and recoverability of DAC for traditional life insurance products and immediate annuities with life contingencies on an aggregate basis. The Company also evaluated these policies on an aggregate basis for circumstances where projected profits would be recognized in early years followed by projected losses in later years. As of September 30, 2017, both traditional life insurance and immediate annuities with life contingencies had projected profit as measured using actual and expected investment holdings and returns; however, the aggregate sufficiency substantially related to traditional life insurance with a marginal sufficiency related to immediate annuities with life contingencies. In conjunction with the segment change in fourth quarter 2017, the Company will review traditional life insurance products and immediate annuities with life contingencies separately.

The Company records an adjustment to the reserve for life-contingent contract benefits that represents the amount by which the reserve balance would increase if the net unrealized gains in the applicable product investment portfolios were realized and reinvested at current lower interest rates, resulting in a premium deficiency. The offset to this liability is recorded as a reduction of the unrealized net capital gains included in accumulated other comprehensive income. As of September 30, 2017, no adjustment was recorded. In conjunction with the segment change in fourth quarter 2017, the Company will evaluate the need for a reserve adjustment separately for traditional life insurance and immediate annuities with life contingencies. The estimated impact, using values as of September 30, 2017, is approximately a $550 million increase to the reserve for life-contingent contract benefits, and a $350 million decrease to unrealized net capital gains, after-tax, included in shareholders’ equity.