Income Taxes	3 Months Ended
Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	(26)Income Taxes Newmark’s unaudited condensed consolidated financial statements include U.S. federal, state and local income taxes on Newmark’s allocable share of its U.S. results of operations, as well as taxes payable to jurisdictions outside the U.S. In addition, certain of Newmark’s entities are taxed as U.S. partnerships and are subject to the Unincorporated Business Tax (“UBT”) in New York City. Therefore, the tax liability or benefit related to the partnership income or loss except for UBT rests with the partners (see Note 2—“Limited Partnership Interests in BGC Holdings and Newmark Holdings” for discussion of partnership interests) rather than the partnership entity. Income taxes are accounted for using the asset and liability method, as prescribed in U.S. GAAP guidance for Income Taxes. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the unaudited condensed consolidated financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. A valuation allowance is recorded against deferred tax assets if it is deemed more likely than not that those assets will not be realized. Provisional amounts in effective rate On December 22, 2017, “H.R.1,” formerly known as the Tax Cuts and Jobs Act of 2017 (the “2017 Tax Act”), was signed into law in the U.S. The 2017 Tax Act is expected to have a favorable impact on Newmark’s effective tax rate and net income as reported under generally accepted accounting principles both in the first quarter of 2018 and subsequent reporting periods to which the 2017 Tax Act is effective. Newmark is applying the guidance in SAB 118 when accounting for the enactment-date effects of the 2017 Tax Act. As of March 31, 2018, Newmark has not completed its accounting for all of the tax effects of the 2017 Tax Act. Newmark will continue to make and refine its calculations as additional analysis is completed. The final impact of the 2017 Tax Act may differ from Newmark’s estimate for the provision for income taxes, possibly materially, due to, among other factors, changes in interpretations, additional guidance that may be issued, unexpected negative changes in business and market conditions that could reduce certain tax benefits, and actions taken by Newmark as a result of the 2017 Tax Act. Because of the complexity of the new Global Intangible Low-Taxed Income (“GILTI”) tax rules, Newmark continues to evaluate this provision of the 2017 Tax Act. Under U.S. GAAP, Newmark can elect an accounting policy choice to either (a) treat future taxes related to GILTI as a current period expense when incurred (“period cost method”) or (b) factor amounts related to GILTI into Newmark’s measurement of its deferred taxes (“deferred method”). Newmark’s accounting for the effects of the GILTI tax law provisions is incomplete at this time, and, therefore, Newmark is not yet able to reasonably estimate the effect of this provision of the 2017 Tax Act nor has an accounting policy decision been made with respect to GILTI. As of March 31, 2018, because Newmark is still evaluating the GILTI provisions as well as future taxable income that may be subject to GILTI, Newmark shall include GILTI related to current-year operations, if any, only in the Estimated Annualized Effective Tax Rate and have not provided additional GILTI on deferred items. Pursuant to U.S. GAAP guidance, Accounting for Uncertainty in Income Taxes, Newmark provides for uncertain tax positions based upon management’s assessment of whether a tax benefit is more likely than not to be sustained upon examination by tax authorities. As of March 31, 2018, Newmark had $0.2 million of unrecognized tax benefits which, if recognized, would affect the effective tax rate. As of December 31, 2017, Newmark’s unrecognized tax benefits, excluding related interest and penalties, were $0.2 million, all of which, if recognized, would affect the effective tax rate. Newmark recognizes interest and penalties related to income tax matters in ”Provision for income taxes”, in Newmark’s unaudited condensed consolidated statements of operations. As of March 31, 2018, Newmark had approximately $45 thousand of accrued interest and penalties related to uncertain tax positions. As of December 31, 2017, there were $45 thousand of accrued interest and penalties related to uncertain tax positions.

(26)Income Taxes

Newmark’s unaudited condensed consolidated financial statements include U.S. federal, state and local income taxes on Newmark’s allocable share of its U.S. results of operations, as well as taxes payable to jurisdictions outside the U.S. In addition, certain of Newmark’s entities are taxed as U.S. partnerships and are subject to the Unincorporated Business Tax (“UBT”) in New York City. Therefore, the tax liability or benefit related to the partnership income or loss except for UBT rests with the partners (see Note 2—“Limited Partnership Interests in BGC Holdings and Newmark Holdings” for discussion of partnership interests) rather than the partnership entity. Income taxes are accounted for using the asset and liability method, as prescribed in U.S. GAAP guidance for Income Taxes. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the unaudited condensed consolidated financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. A valuation allowance is recorded against deferred tax assets if it is deemed more likely than not that those assets will not be realized.

Provisional amounts in effective rate

On December 22, 2017, “H.R.1,” formerly known as the Tax Cuts and Jobs Act of 2017 (the “2017 Tax Act”), was signed into law in the U.S. The 2017 Tax Act is expected to have a favorable impact on Newmark’s effective tax rate and net income as reported under generally accepted accounting principles both in the first quarter of 2018 and subsequent reporting periods to which the 2017 Tax Act is effective. Newmark is applying the guidance in SAB 118 when accounting for the enactment-date effects of the 2017 Tax Act. As of March 31, 2018, Newmark has not completed its accounting for all of the tax effects of the 2017 Tax Act. Newmark will continue to make and refine its calculations as additional analysis is completed. The final impact of the 2017 Tax Act may differ from Newmark’s estimate for the provision for income taxes, possibly materially, due to, among other factors, changes in interpretations, additional guidance that may be issued, unexpected negative changes in business and market conditions that could reduce certain tax benefits, and actions taken by Newmark as a result of the 2017 Tax Act.

Because of the complexity of the new Global Intangible Low-Taxed Income (“GILTI”) tax rules, Newmark continues to evaluate this provision of the 2017 Tax Act. Under U.S. GAAP, Newmark can elect an accounting policy choice to either (a) treat future taxes related to GILTI as a current period expense when incurred (“period cost method”) or (b) factor amounts related to GILTI into Newmark’s measurement of its deferred taxes (“deferred method”). Newmark’s accounting for the effects of the GILTI tax law provisions is incomplete at this time, and, therefore, Newmark is not yet able to reasonably estimate the effect of this provision of the 2017 Tax Act nor has an accounting policy decision been made with respect to GILTI. As of March 31, 2018, because Newmark is still evaluating the GILTI provisions as well as future taxable income that may be subject to GILTI, Newmark shall include GILTI related to current-year operations, if any, only in the Estimated Annualized Effective Tax Rate and have not provided additional GILTI on deferred items.

Pursuant to U.S. GAAP guidance, Accounting for Uncertainty in Income Taxes, Newmark provides for uncertain tax positions based upon management’s assessment of whether a tax benefit is more likely than not to be sustained upon examination by tax authorities. As of March 31, 2018, Newmark had $0.2 million of unrecognized tax benefits which, if recognized, would affect the effective tax rate. As of December 31, 2017, Newmark’s unrecognized tax benefits, excluding related interest and penalties, were $0.2 million, all of which, if recognized, would affect the effective tax rate. Newmark recognizes interest and penalties related to income tax matters in ”Provision for income taxes”, in Newmark’s unaudited condensed consolidated statements of operations. As of March 31, 2018, Newmark had approximately $45 thousand of accrued interest and penalties related to uncertain tax positions. As of December 31, 2017, there were $45 thousand of accrued interest and penalties related to uncertain tax positions.