Annual report pursuant to Section 13 and 15(d)

Marketable Securities - Additional Information (Detail)

v3.10.0.1
Marketable Securities - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Asset-backed Securities [Member] | Maximum [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Remaining contractual maturities of marketable securities 1 year 1 year  
U.S. and Foreign Commercial Paper [Member] | Maximum [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Remaining contractual maturities of marketable securities 1 year 1 year  
U.S. and Foreign Corporate Debt Securities [Member] | Maximum [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Remaining contractual maturities of marketable securities 1 year 1 year  
U.S. Treasury Securities [Member] | Maximum [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Remaining contractual maturities of marketable securities 1 year 1 year  
Debt Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Realized gains and losses $ 0 $ 0 $ 0
Marketable investments continuous unrealized loss position $ 0 $ 0