XML 57 R38.htm IDEA: XBRL DOCUMENT v3.19.3
Marketable Securities - Additional Information (Details) - USD ($)
9 Months Ended 12 Months Ended
Sep. 30, 2019
Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]    
Gross unrealized loss $ 1,000 $ 104,000