Revenue Recognition - Additional Information (Details)			3 Months Ended		7 Months Ended	9 Months Ended
		Mar. 07, 2019 Segment	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) Segment Program Obligation Source	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Disaggregation Of Revenue [Line Items]
Number of reportable segments | Segment		1				2
Revenue, Practical Expedient, Initial Application and Transition, Qualitative Assessment						true
Revenue	[1]		$ 254,909,000	$ 303,897,000		$ 855,162,000	$ 858,369,000
Healthcare
Disaggregation Of Revenue [Line Items]
Number of programs | Program						3
Number of performance obligations | Obligation						1
Number of performance obligation unsatisfied | Obligation						0
Revenue recognized from performance obligations satisfied in prior period			0			$ 0
Period of billing in arrears once timing of services to customers is known						1 month
Number of days for customer to make payment after being invoiced						30 days
Capitalized costs			700,000			$ 700,000		$ 500,000
Capitalized costs amortization			100,000			$ 200,000
Number of reportable segments | Segment						2
Revenue			$ 95,481,000	$ 159,979,000		$ 337,096,000	473,987,000
Healthcare | SilverSneakers
Disaggregation Of Revenue [Line Items]
Revenues from PMPM fees percentage			59.00%	33.00%
Revenue			$ 68,613,000	$ 124,602,000		$ 239,377,000	370,524,000
Nutrition
Disaggregation Of Revenue [Line Items]
Number of sources for revenue recognition | Source						4
Description of return of obligation						Direct to consumer customers may return unopened ready-to-go Nutrisystem products within 30 days after purchase in order to receive a refund or credit.
Return of purchase order to refund or credit, period						30 days
Purchase order canceled of delivery, period						14 days
Revenue			159,428,000	143,918,000		$ 518,066,000	$ 384,382,000
Provision for estimated returns			3,700,000	3,900,000	$ 11,000,000.0	13,000,000.0
Nutrition | Accrued Liabilities
Disaggregation Of Revenue [Line Items]
Reserve for estimated returns			1,200,000			1,200,000		$ 800,000
Nutrition | Shipping and Handling Charges
Disaggregation Of Revenue [Line Items]
Revenue			$ 5,800,000	$ 5,300,000	$ 13,400,000	$ 18,700,000

[1] The figure for total segments equals the consolidated figure for such item.