Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Indefinite Lived Intangible Assets By Major Class [Line Items]
Intangible asset impairment		$ 3.8	$ 70.1	$ 3.8
In- Process Research and Development [Member]
Indefinite Lived Intangible Assets By Major Class [Line Items]
Intangible asset impairment	$ 70.1
Licensing Arrangements from Unrelated Third Party [Member]
Indefinite Lived Intangible Assets By Major Class [Line Items]
Payment to acquire licensing arrangements from an unrelated third party	$ 192.5