Formation and Business of the Company - Additional Information - Public Offering (Detail) - USD ($)	1 Months Ended			12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Nov. 30, 2014	Dec. 31, 2018
Subsidiary, Sale of Stock [Line Items]
Net proceeds from common stock		$ 118,400,000	$ 131,600,000
1.75% Convertible Senior Notes due 2021 [Member]
Subsidiary, Sale of Stock [Line Items]
Aggregate principal amount of convertible senior notes	$ 150,000,000
Debt instrument interest rate	1.75%			1.75%
Debt instrument due year	2021			2021
Additional aggregate principal amount of convertible senior notes	$ 22,500,000
Debt instrument frequency of payment				semi-annually in arrears on June 1 and December 1 of each year, commencing on December 1, 2016
Net proceeds from the debt offering after deducting transaction costs	$ 166,200,000
Common Stock [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued		2,470,587
IPO [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued			8,050,000
Common stock, shares issued price per share			$ 18.00
IPO [Member] | Common Stock [Member]
Subsidiary, Sale of Stock [Line Items]
Shares issued upon conversion of redeemable convertible preferred stock and convertible preferred stock			15,208,048
Over Allotment Option [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued		705,882	1,050,000