Summary of Significant Accounting Policies (Policies)	9 Months Ended
Sep. 30, 2019
Summary of Significant Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation - The accompanying unaudited condensed consolidated financial statements of Medifast, Inc. and its wholly-owned subsidiaries (the “Company,” “we,” “us,” or “our”) included herein have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) for interim reporting and pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Accordingly, certain information and notes that are normally required by GAAP have been condensed or omitted. However, in the opinion of management, all adjustments consisting of normal, recurring adjustments considered necessary for a fair presentation of the financial position and results of operations have been included and management believes the disclosures that are made are adequate to make the information presented not misleading. The condensed consolidated balance sheet at December 31, 2018 has been derived from the audited consolidated financial statements at that date. The results of operations for the three and nine months ended September 30, 2019 are not necessarily indicative of results that may be expected for the fiscal year ending December 31, 2019. The accompanying unaudited condensed consolidated financial statements should be read in conjunction with the 2018 audited consolidated financial statements and notes thereto, which are included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2018 (“2018 Form 10-K”).
Presentation of Financial Statements	Presentation of Financial Statements - The unaudited condensed consolidated financial statements included herein include the accounts of the Medifast, Inc. and its wholly-owned subsidiaries. All significant intercompany accounts and transactions have been eliminated.
Reclassification	Reclassification - Certain amounts reported for prior periods have been reclassified to be consistent with the current period presentation. No reclassification in the consolidated financial statements had a material impact on the presentation.
Use of Estimates	Use of Estimates - The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenue and expenses during the reporting period. Actual results could differ materially from those estimates.
Recent Accounting Pronouncements	Accounting Pronouncements Adopted in 2019 – In February 2018, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220) to address a specific consequence of the Tax Cuts and Jobs Act (“TCJA”) by allowing a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the TCJA’s reduction of the U.S. federal corporate income tax rate. This ASU was effective for all entities for annual periods beginning after December 15, 2018, with early adoption permitted, and was to be applied either in the period of adoption or retrospectively to each period in which the effect of the change in the U.S. federal corporate income tax rate in the TCJA is recognized. The Company adopted this ASU in the first quarter of 2019. There was no material impact on the Company's condensed consolidated results of operations or cash flows. The Company's policy for releasing disproportionate income tax effects from accumulated other comprehensive income utilizes the portfolio approach. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which requires an entity to recognize a right-of-use (“ROU”) asset and a lease liability on the balance sheet for all leases, including operating leases, and also requires disclosures about the amount, timing and uncertainty of cash flows arising from leases. Subsequent to the issuance of Topic 842, the FASB clarified the guidance through several ASUs; hereinafter the collection of lease guidance is referred to as “ASC 842.” On January 1, 2019, the Company adopted ASC 842 using the modified retrospective method for all lease arrangements at the beginning of the period of adoption. Results for reporting periods beginning January 1, 2019 are presented under ASC 842, while prior period amounts were not adjusted and continue to be reported in accordance with the Company’s historic accounting under ASC 840, Leases. The standard had a material impact on the Company’s Condensed Consolidated Balance Sheets, but did not have a significant impact on the Company’s consolidated net earnings and cash flows. The most significant impact was the recognition of ROU assets and lease liabilities for operating leases. For leases that commenced before the effective date of ASC 842, the Company elected the permitted practical expedients that do not require the Company to reassess: (i) whether any expired or existing contracts contain leases; (ii) the lease classification for any expired or existing leases; and (iii) initial direct costs for any existing leases. The Company also elected to exclude leases with a term of 12 months or less in the recognized ROU assets and lease liabilities. As a result of the cumulative impact of adopting ASC 842, the Company recorded ROU assets of $11.9 million, net of $686 thousand of accrued rent, and lease liabilities of $12.6 million as of January 1, 2019, primarily related to office and warehouse space and certain equipment, based on the present value of the future lease payments on the date of adoption. The Company determines if an arrangement is a lease at inception. The ROU assets represent the Company’s right to use an underlying asset for the lease term, and lease liabilities represent an obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit interest rate, the Company uses its incremental borrowing rate based on the information available at the lease commencement date in determining the present value of lease payments. The ROU asset also consists of any prepaid lease payments and lease incentives received. The lease terms used to calculate the ROU asset and related lease liability include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for operating leases is recognized on a straight-line basis over the lease term as an operating expense. See Note 5 “LEASES” for additional information about this adoption. Recently Issued Accounting Pronouncements – In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40), which addresses the accounting for implementation costs associated with a hosted service. The standard provides amendments to align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal use software license). This ASU is effective for fiscal years beginning after December 15, 2019, with early adoption permitted. Management is currently evaluating the effect that the provisions of ASU 2018-15 will have on the Company’s consolidated financial statements.

Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2019

Summary of Significant Accounting Policies [Abstract]

Basis of Presentation - The accompanying unaudited condensed consolidated financial statements of Medifast, Inc. and its wholly-owned subsidiaries (the “Company,” “we,” “us,” or “our”) included herein have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) for interim reporting and pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Accordingly, certain information and notes that are normally required by GAAP have been condensed or omitted. However, in the opinion of management, all adjustments consisting of normal, recurring adjustments considered necessary for a fair presentation of the financial position and results of operations have been included and management believes the disclosures that are made are adequate to make the information presented not misleading. The condensed consolidated balance sheet at December 31, 2018 has been derived from the audited consolidated financial statements at that date.

The results of operations for the three and nine months ended September 30, 2019 are not necessarily indicative of results that may be expected for the fiscal year ending December 31, 2019. The accompanying unaudited condensed consolidated financial statements should be read in conjunction with the 2018 audited consolidated financial statements and notes thereto, which are included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2018 (“2018 Form 10-K”).

Presentation of Financial Statements

Presentation of Financial Statements - The unaudited condensed consolidated financial statements included herein include the accounts of the Medifast, Inc. and its wholly-owned subsidiaries. All significant intercompany accounts and transactions have been eliminated.

Reclassification

Reclassification - Certain amounts reported for prior periods have been reclassified to be consistent with the current period presentation. No reclassification in the consolidated financial statements had a material impact on the presentation.

Use of Estimates

Use of Estimates - The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenue and expenses during the reporting period. Actual results could differ materially from those estimates.

Recent Accounting Pronouncements

Accounting Pronouncements Adopted in 2019 – In February 2018, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220) to address a specific consequence of the Tax Cuts and Jobs Act (“TCJA”) by allowing a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the TCJA’s reduction of the U.S. federal corporate income tax rate. This ASU was effective for all entities for annual periods beginning after December 15, 2018, with early adoption permitted, and was to be applied either in the period of adoption or retrospectively to each period in which the effect of the change in the U.S. federal corporate income tax rate in the TCJA is recognized. The Company adopted this ASU in the first quarter of 2019. There was no material impact on the Company's condensed consolidated results of operations or cash flows. The Company's policy for releasing disproportionate income tax effects from accumulated other comprehensive income utilizes the portfolio approach.

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which requires an entity to recognize a right-of-use (“ROU”) asset and a lease liability on the balance sheet for all leases, including operating leases, and also requires disclosures about the amount, timing and uncertainty of cash flows arising from leases. Subsequent to the issuance of Topic 842, the FASB clarified the guidance through several ASUs; hereinafter the collection of lease guidance is referred to as “ASC 842.”

On January 1, 2019, the Company adopted ASC 842 using the modified retrospective method for all lease arrangements at the beginning of the period of adoption. Results for reporting periods beginning January 1, 2019 are presented under ASC 842, while prior period amounts were not adjusted and continue to be reported in accordance with the Company’s historic accounting under ASC 840, Leases. The standard had a material impact on the Company’s Condensed Consolidated Balance Sheets, but did not have a significant impact on the Company’s consolidated net earnings and cash flows. The most significant impact was the recognition of ROU assets and lease liabilities for operating leases. For leases that commenced before the effective date of ASC 842, the Company elected the permitted practical expedients that do not require the Company to reassess: (i) whether any expired or existing contracts contain leases; (ii) the lease classification for any expired or existing leases; and (iii) initial direct costs for any existing leases. The Company also elected to exclude leases with a term of 12 months or less in the recognized ROU assets and lease liabilities.

As a result of the cumulative impact of adopting ASC 842, the Company recorded ROU assets of $11.9 million, net of $686 thousand of accrued rent, and lease liabilities of $12.6 million as of January 1, 2019, primarily related to office and warehouse space and certain equipment, based on the present value of the future lease payments on the date of adoption.

The Company determines if an arrangement is a lease at inception. The ROU assets represent the Company’s right to use an underlying asset for the lease term, and lease liabilities represent an obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit interest rate, the Company uses its incremental borrowing rate based on the information available at the lease commencement date in determining the present value of lease payments. The ROU asset also consists of any prepaid lease payments and lease incentives received. The lease terms used to calculate the ROU asset and related lease liability include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for operating leases is recognized on a straight-line basis over the lease term as an operating expense. See Note 5 “LEASES” for additional information about this adoption.

Recently Issued Accounting Pronouncements – In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40), which addresses the accounting for implementation costs associated with a hosted service. The standard provides amendments to align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal use software license). This ASU is effective for fiscal years beginning after December 15, 2019, with early adoption permitted. Management is currently evaluating the effect that the provisions of ASU 2018-15 will have on the Company’s consolidated financial statements.