Cash, Cash Equivalents and Marketable Securities - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2017 USD ($) Investment	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)
Cash, cash equivalents and marketable securities [Line Items]
Long-term marketable securities, minimum original maturity term	1 year
Marketable securities, average remaining contractual maturity period	2 months 9 days
Long-term marketable securities	$ 0		$ 0
Number of debt securities in unrealized loss positions | Investment	7
Debt securities in unrealized loss positions, total unrealized loss	$ 2,000
Debt securities in unrealized loss positions, total fair market value	3,946,000
Credit risk	0
Gain (loss) on investments	$ 0	$ 0
Minimum
Cash, cash equivalents and marketable securities [Line Items]
Short-term marketable securities, minimum original maturity term	90 days