Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company’s effective tax rate increased to 20.8% for the nine months ended September 30, 2020 from 12.6% for the nine months ended September 30, 2019. The effective tax rate for the nine months ended September 30, 2020 includes discrete tax benefits primarily related to a prior year R&D credit true-up and net equity compensation deductions. For the nine months ended September 30, 2020, the differences between the federal statutory rate and our effective tax rate are tax expense items related to state taxes, equity compensation impacts, unrecognized tax benefits, including interest, officer compensation deduction limits, research and development tax credits, and other permanent differences. The Company has current period foreign income tax expense and includes global intangible low-taxed income as current period income tax expense, both of which are not material to the overall financial statements. Included in Other liabilities on the Consolidated Balance Sheets, are the total amount of unrecognized tax benefits (net of the federal benefit for state issues) of approximately $5.3 million and $4.2 million, as of September 30, 2020 and December 31, 2019, respectively, that, if recognized, would favorably affect the Company’s future effective tax rate. Also included in Other liabilities on the Consolidated Balance Sheets, are accrued liabilities for interest expense and penalties related to unrecognized tax benefits of $0.9 million and $0.7 million as of September 30, 2020 and December 31, 2019, respectively. HMS includes interest expense and penalties in the provision for income taxes in the unaudited Consolidated Statements of Income. The amount of interest expense (net of federal and state income tax benefits) and penalties in the unaudited Consolidated Statements of Income for the nine months ended September 30, 2020 and 2019 was $0.2 million and $0.03 million, respectively. The Company believes it is reasonably possible that the amount of unrecognized tax benefits may decrease by $1.6 million over the next twelve months, due to the expiration of the statute of limitations in federal and various state jurisdictions. HMS files income tax returns with the U.S. Federal government and various state and local jurisdictions and will file income tax returns in certain foreign jurisdictions in future periods as a result of its acquisition of VitreosHealth. HMS is generally no longer subject to U.S. Federal income tax examinations for years before 2016. HMS operates in a number of state, local and foreign jurisdictions. Accordingly, HMS is subject to state, local and foreign income tax examinations based on the various statutes of limitations in each jurisdiction. On March 27, 2020, the Coronavirus Aid, Relief and Economic Security Act ("CARES Act") was enacted in response to the COVID-19 pandemic. The CARES Act includes numerous provisions relating to, among other things, refundable payroll tax credits, deferment of the employer portion of certain payroll taxes, net operating loss amounts and carryback periods, alternative minimum tax credit refunds, modifications to the net interest deduction limitations and technical corrections to tax depreciation methods for qualified improvement property. The Company continues to analyze the potential impacts of this legislation on its financial position and results of operations.

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.