Revenue Recognition - Summary of Revenue Disaggregated by Program (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Disaggregation Of Revenue [Line Items]
Revenues	$ 214,094	$ 149,930
Healthcare
Disaggregation Of Revenue [Line Items]
Revenues	156,527	149,930
Healthcare \| SilverSneakers
Disaggregation Of Revenue [Line Items]
Revenues	123,024	120,925
Healthcare \| Prime Fitness
Disaggregation Of Revenue [Line Items]
Revenues	28,743	24,734
Healthcare \| WholeHealth Living
Disaggregation Of Revenue [Line Items]
Revenues	4,575	4,217
Healthcare \| Other
Disaggregation Of Revenue [Line Items]
Revenues	$ 185	$ 54

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045

Name:	us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration