Revenue Recognition - Summary of Revenue Disaggregated by Program (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation Of Revenue [Line Items]
Revenue	[1]	$ 254,909	$ 303,897	$ 855,162	$ 858,369
Other
Disaggregation Of Revenue [Line Items]
Revenue				6,800
Healthcare
Disaggregation Of Revenue [Line Items]
Revenue		95,481	159,979	337,096	473,987
Healthcare | SilverSneakers
Disaggregation Of Revenue [Line Items]
Revenue		68,613	124,602	239,377	370,524
Healthcare | Prime Fitness
Disaggregation Of Revenue [Line Items]
Revenue		21,687	30,499	73,545	88,993
Healthcare | WholeHealth Living
Disaggregation Of Revenue [Line Items]
Revenue		5,040	4,752	14,835	13,783
Healthcare | Other
Disaggregation Of Revenue [Line Items]
Revenue	[2]	$ 141	$ 126	$ 9,339	$ 687

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

[2] For the nine months ended September 30, 2020, other revenue in the table above includes $6.8 million from a well-being program with a large employer. For the three and nine months ended September 30, 2020, other revenue in the table above also includes $0.1 million and $2.2 million, respectively, of Wisely Well revenue.