Income taxes	9 Months Ended
Income taxes	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income taxes	Income taxes The Company and its Bermuda-domiciled subsidiaries are not subject to Bermuda income tax under current Bermuda law. In the event there is a change in the current law such that taxes are imposed, the Company and its Bermuda-domiciled subsidiaries would be exempt from such tax until March 31, 2035, pursuant to the Bermuda Exempted Undertakings Tax Protection Act of 1966. The Company has subsidiaries and branches that operate in various other jurisdictions around the world that are subject to tax in the jurisdictions in which they operate. The jurisdictions in which the Company's subsidiaries and branches are subject to tax are Australia, Belgium, Canada, Denmark, Germany, Gibraltar, Hong Kong (China), Ireland, Luxembourg, Malaysia, Shanghai (China), Singapore, Spain, Sweden, Switzerland, the United Kingdom, and the United States. For the three month period ended September 30, 2020, Sirius Group reported an income tax expense (benefit) of $23.5 million on pre-tax income (loss) of $(80.5) million. The difference between the effective tax rate on income from continuing operations and the Swedish statutory tax rate of 21.4% (the rate at which the majority of Sirius Group's worldwide operations are taxed) is primarily attributable to unrealized investment gains in specific U.S. entities and adjustments required under applicable GAAP guidance, which are based on the annual estimated effective tax rate. For the nine month period ended September 30, 2020, Sirius Group reported an income tax expense (benefit) of $19.9 million on pre-tax income (loss) of $(212.6) million. The difference between the effective tax rate for the nine months ended September 30, 2020 and the Swedish statutory rate of 21.4% was primarily attributable to valuation allowances recorded against certain deferred tax assets, unrealized investment gains in specific U.S. entities, and adjustments required under applicable GAAP guidance, which are based on the annual estimated effective tax rate. For the three month period ended September 30, 2019, Sirius Group reported an income tax (benefit) of $(3.7) million on pre-tax (loss) of $(11.3) million. The effective tax rate was higher than the Swedish statutory tax rate of 21.4% primarily because of income recognized in jurisdictions with higher rates than Sweden and adjustments required under applicable GAAP guidance, which are based on the annual estimated effective tax rate. For the nine month period ended September 30, 2019, Sirius Group reported an income tax expense of $15.6 million on pre-tax income of $120.3 million. The effective tax rate for the nine months ended September 30, 2019 was lower than the Swedish statutory rate of 21.4% primarily because of income recognized in countries with lower rates than Sweden and adjustments required under applicable GAAP guidance, which are based on the annual estimated effective tax rate. For purposes of estimating the annual effective tax rate for the nine month periods ended September 30, 2020 and 2019, respectively, Sirius Group took into consideration all year-to-date income and expense items including the change in unrealized investment gains (losses) and realized investment gains (losses) and such items on a forecasted basis for the remainder of each year. Based on applicable GAAP guidance, jurisdictions with a projected loss for the full year where no tax benefit can be recognized are excluded from the estimation of the annual effective tax rate. The Tax Cuts and Jobs Act ("TCJA") includes a new Base Erosion and Anti-Abuse Minimum Tax ("BEAT") provision, which is essentially a minimum tax that is potentially applicable to certain otherwise deductible payments made by U.S. entities to non-U.S. affiliates, including cross-border interest payments and reinsurance premiums. The statutory BEAT rate is 10% in 2019-2025, and then rises to 12.5% in 2026 and thereafter. The TCJA also includes provisions for Global Intangible Low-Taxed Income ("GILTI") under which taxes on foreign income are imposed on the excess of a deemed return on tangible assets of certain foreign subsidiaries. Consistent with accounting guidance, Sirius Group will treat BEAT as an in period tax charge when incurred in future periods for which no deferred taxes need to be provided and has made an accounting policy election to treat GILTI taxes in a similar manner. No provision for income taxes related to BEAT or GILTI was recorded as of September 30, 2020 and December 31, 2019. Sirius Group has capital and liquidity in many of its subsidiaries, some of which may reflect undistributed earnings. If such capital or liquidity were to be paid or distributed to the Company or Sirius Group's subsidiaries, as dividends or otherwise, they may be subject to income or withholding taxes. Sirius Group generally intends to operate, and manage its capital and liquidity, in a tax-efficient manner. However, the applicable tax laws in relevant countries are still evolving, including in connection with guidance and proposals from the Organisation for Economic Cooperation and Development. Accordingly, such payments or earnings may be subject to income or withholding tax in jurisdictions where they are not currently taxed or at higher rates of tax than currently taxed, and the applicable tax authorities could attempt to apply income or withholding tax to past earnings or payments. In April 2020, the European Court of Justice (the “ECJ”) published a decision disallowing the eligibility of an unrelated Gibraltar company for a European Union directive providing relief from withholding taxes on cross-border dividends. More generally, as a result of Brexit, it is projected that Gibraltar companies will cease to be eligible for European Union tax directives from January 1, 2021. The Company has a subsidiary organized in Gibraltar which has been a party to cross-border transactions with affiliates. The Company has assessed the tax consequences of these developments and concluded that they should not materially impact the Company’s provision for income taxes. Deferred tax asset, net of valuation allowance Sirius Group's net deferred tax liability, net of the valuation allowance as of September 30, 2020 is $55.1 million. Of the $55.1 million, $25.0 million relates to net deferred tax assets in U.S. subsidiaries, $141.3 million relates to net deferred tax assets in Luxembourg subsidiaries, $213.8 million relates to net deferred tax liabilities in Sweden subsidiaries, and $7.6 million relates to other net deferred tax liability. Sirius Group records a valuation allowance against deferred tax assets if it becomes more likely than not that all or a portion of a deferred tax asset will not be realized. Changes in valuation allowances from period to period are included in income tax expense in the period of change. In determining whether or not a valuation allowance, or change therein, is warranted, Sirius Group considers factors such as prior earnings history, expected future earnings, carryback and carryforward periods and strategies that if executed would result in the realization of a deferred tax asset. It is possible that certain planning strategies or projected earnings in certain subsidiaries may not be feasible to utilize the entire deferred tax asset, which could result in material changes to Sirius Group's deferred tax assets and tax expense. Uncertain tax positions Recognition of the benefit of a given tax position is based upon whether a company determines that it is more likely than not that a tax position will be sustained upon examination based upon the technical merits of the position. In evaluating the more likely than not recognition threshold, Sirius Group must presume that the tax position will be subject to examination by a taxing authority with full knowledge of all relevant information. If the recognition threshold is met, then the tax position is measured at the largest amount of benefit that is more than 50% likely of being realized upon ultimate settlement. As of September 30, 2020, the total reserve for unrecognized tax benefits is $47.5 million. If Sirius Group determines in the future that its reserves for unrecognized tax benefits on permanent differences and interest and penalties are not needed, the reversal of $47.3 million of such reserves as of September 30, 2020 would be recorded as an income tax benefit and would impact the effective tax rate. If Sirius Group determines in the future that its reserves for unrecognized tax benefits on temporary differences are not needed, the reversal of $0.2 million of such reserves as of September 30, 2020 would not impact the effective tax rate due to deferred tax accounting but would accelerate the payment of cash to the taxing authority. Most of Sirius Group's reserves for unrecognized tax benefits on permanent differences relate to interest deductions denied by the Swedish Tax Authority ("STA"), as described further below. The STA has denied deductions claimed by two of the Company's Swedish subsidiaries in certain tax years for interest paid on intra-group debt instruments. Sirius Group has challenged the STA's denial in court based on the technical merits. In October 2018, one of the Swedish subsidiaries received an adverse decision from Sweden's Administrative Court, which Sirius Group has appealed. Sirius Group has taken into account this and other relevant developments in applicable Swedish tax law and has established a reserve for this uncertain tax position. As of September 30, 2020, the total amount of such reserve was $46.6 million. In connection with this matter, Sirius Group has also taken into account the Stock Purchase Agreement ("SPA") by which Sirius Group was sold to CMIG International Holding Pte. Ltd ("CMIG International") in 2016 and has recorded an indemnification asset. Pursuant to the SPA, the seller agreed to indemnify the buyer and Sirius Group for, among other things, (1) any additional tax liability in excess of Sirius Group's accounting for uncertain tax positions for tax periods prior to the sale of Sirius Group to CMIG International, and (2) an impairment in Sirius Group's net deferred tax assets resulting from a final determination by a tax authority. CMIG International has informed Sirius Group of their view that CMIG International, rather than Sirius Group, should be entitled to all of the proceeds of such an indemnification claim, while Sirius Group is of the view that it should be entitled to the proceeds of such an indemnification claim to the extent of the book value of the relevant deferred tax assets, and therefore, Sirius Group continues to carry the related indemnification asset on the balance sheet. While Sirius Group intends to continue challenging the STA's denial based on the technical merits (including appealing the adverse court decision received in October 2018), the ultimate resolution of these tax disputes is uncertain and no assurance can be given that there will be no material changes to Sirius Group's operating results or balance sheet in connection with these uncertain tax positions or the related indemnification. With few exceptions, Sirius Group is no longer subject to U.S. federal, state or non-U.S. income tax examinations by tax authorities for years before 2015.

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.