Transactions - Passport (Details) shares in Millions, beneficiary in Millions		12 Months Ended
	Feb. 01, 2016 USD ($) beneficiary shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Increase (decrease) in contingent consideration liability		$ (4,104,000)	$ 400,000	$ (2,086,000)
Tangible assets acquired:
Goodwill		768,124,000	628,186,000	$ 626,569,000
Passport
Business Acquisition [Line Items]
Number of medicaid and medicare advantage beneficiaries | beneficiary	0.3
Additional equity consideration (up to)	$ 10,000,000.0
Term of health plan management and managed care services arrangement	10 years
Transaction costs	$ 300,000
Contingent consideration, liability	7,800,000	5,600,000
Increase (decrease) in contingent consideration liability		$ (3,100,000)	$ 400,000
Purchase consideration:
Fair value of Class A common stock issued	10,450,000
Fair value of contingent consideration	7,750,000
Total consideration	18,200,000
Tangible assets acquired:
Prepaid asset	6,900,000
Goodwill	11,300,000
Net assets acquired	$ 18,200,000
Passport | Class A | Common Stock
Business Acquisition [Line Items]
Issuance of common stock (in shares) | shares	1.1