Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Schedule Of Significant Accounting Policies [Line Items]
Performance obligation, description of timing	Collection of consideration the Company expects to receive typically occurs within 30 to 60 days of billing for commercial insurance, Medicare and other governmental and self-pay payers and within 60 to 90 days of billing for client payers.
Cost of revenue	$ 211,994,000	$ 149,476,000	$ 138,295,000
Impairment of long-lived assets held-for-use	0	0	0
Operating lease right-of-use assets	26,492,000			$ 9,700,000
Operating lease, liability	$ 27,415,000			$ 10,100,000
Software and Software Development Costs | Minimum
Schedule Of Significant Accounting Policies [Line Items]
Estimated Useful Lives in Years	2 years
Software and Software Development Costs | Maximum
Schedule Of Significant Accounting Policies [Line Items]
Estimated Useful Lives in Years	10 years
Shipping costs
Schedule Of Significant Accounting Policies [Line Items]
Cost of revenue	$ 14,200,000	$ 9,800,000	$ 10,800,000