Summary of Significant Accounting Policies - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 01, 2016
Significant Accounting Policies [Line Items]
Outstanding standby letters of credit as collateral		$ 19,600,000	$ 19,600,000	$ 20,200,000
Accrued revenue		41,800,000	41,800,000	41,200,000
Equity compensation			4,100,000	3,400,000	$ 2,500,000
Advertising costs			7,600,000	10,200,000	4,900,000
Prepaid expenses, advertising		0	0	0
Cumulative impact of currency fluctuations		1,200,000	1,200,000	1,200,000
Income tax expense related to deferred tax asset		8,000,000	200,000
Income tax expense (benefit) related to items of other comprehensive (loss) income				0	$ 200,000
Occurrence-Based Professional Liability Insurance | MDA Holdings Inc
Significant Accounting Policies [Line Items]
Coverage for professional liability claims	$ 500,000.0
Claims-Based Liability Insurance
Significant Accounting Policies [Line Items]
Self insured retention claim per policy						$ 500,000
Claims-Based Liability Insurance | MDA Holdings Inc
Significant Accounting Policies [Line Items]
Letter of credit for malpractice claims		$ 2,000,000	$ 2,000,000	$ 2,000,000
Minimum
Significant Accounting Policies [Line Items]
Contract terms			15 days
Short term leases period			3 months
Estimated useful life of assets			3 years
Intangible assets- useful life			1 year
Minimum | Computer software
Significant Accounting Policies [Line Items]
Estimated useful life of assets			3 years
Maximum
Significant Accounting Policies [Line Items]
Contract terms			60 days
Short term leases period			6 months
Estimated useful life of assets			7 years
Intangible assets- useful life			16 years
Maximum | Computer software
Significant Accounting Policies [Line Items]
Estimated useful life of assets			5 years