Marketable Securities - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2017
Schedule of Available-for-sale Securities [Line Items]
Weighted-average remaining maturity period of marketable debt securities, months	15 months
Minimum
Schedule of Available-for-sale Securities [Line Items]
Remaining maturities of marketable debt securities	2017-07
Maximum
Schedule of Available-for-sale Securities [Line Items]
Remaining maturities of marketable debt securities	2020-09