Organization and Capitalization - Additional Information (Detail) - USD ($)	1 Months Ended
	Dec. 31, 2017	Mar. 31, 2019	Dec. 31, 2018	Dec. 06, 2013
Organization And Capitalization [Line Items]
Common stock, shares authorized		750,000,000	750,000,000
Preferred stock, shares authorized				25,000,000
Preferred stock, par value (in dollars per share)				$ 0.01
Minimum [Member]
Organization And Capitalization [Line Items]
Common stock, shares authorized				225,000,000
Maximum [Member]
Organization And Capitalization [Line Items]
Common stock, shares authorized				750,000,000
China National Scientific and Instruments and Materials Company [Member]
Organization And Capitalization [Line Items]
Proceeds from distribution agreement	$ 15,000,000
Distribution minimum royalties payment	14,000,000
China National Scientific and Instruments and Materials Company [Member] | Minimum [Member]
Organization And Capitalization [Line Items]
Expected proceeds from distribution agreement	$ 29,000,000