Summary of Significant Accounting Policies - Narrative (Detail)	1 Months Ended	12 Months Ended
	Mar. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) reporting_unit	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Significant Accounting Policies [Line Items]
Number of reporting units | reporting_unit		4
Outstanding standby letters of credit as collateral		$ 20,200,000	$ 21,500,000
Accrued revenue		41,200,000	18,400,000
Equity compensation		3,400,000	2,500,000	$ 1,400,000
Advertising costs		10,200,000	4,900,000	4,100,000
Prepaid expenses, advertising		0	0
Cumulative impact of currency fluctuations		1,200,000	1,200,000
Income tax expense (benefit) related to items of other comprehensive (loss) income		0	0	$ 162,000
Claims-Based Liability Insurance | MDA Holdings Inc
Significant Accounting Policies [Line Items]
Letter of credit for malpractice claims		2,000,000
Occurrence-Based Professional Liability Insurance | MDA Holdings Inc
Significant Accounting Policies [Line Items]
Coverage for professional liability claims	$ 500,000.0
Letter of credit for malpractice claims			2,000,000
Other Current Liabilities
Significant Accounting Policies [Line Items]
Deferred revenue		$ 900,000	1,100,000
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
ASU 2015-03 | Long-term Debt and Capital Lease Obligations
Significant Accounting Policies [Line Items]
Debt issuance costs, net			$ 500,000