XML 41 R38.htm IDEA: XBRL DOCUMENT v3.20.1
Marketable Securities - Schedule of Amortized Cost, Gross Unrealized Holding Losses and Fair Value of Available-for-Sale Debt Securities by Type of Security (Detail) - USD ($)
Mar. 31, 2020
Dec. 31, 2019
Available for sale securities:    
Fair Value   $ 0
U.S. Government-Related Obligations [Member]    
Available for sale securities:    
Amortized Cost $ 227,419,000  
Gross Unrealized Holding Gains 1,394,000  
Fair Value $ 228,813,000