Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jul. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Accrued other long-term liabilities	$ 4.5		$ 4.5
Estimated sales and marketing expense	0.3	$ 0.2	1.0	$ 0.8
Freezing amount in cash resulted from court pending legal action issued	0.7		0.7		$ 2.5
Accruals related court pending legal dispute	$ 1.6		$ 1.6