XML 65 R55.htm IDEA: XBRL DOCUMENT v3.19.3
Cash and Marketable Securities (Narrative) (Details) - USD ($)
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Dec. 31, 2018
Cash and Marketable Securities [Abstract]          
Marketable Securities, Realized Gain (Loss) $ 0 $ 0 $ 0 $ 0  
Impairment charges due to declines in the vale of debt securities $ 0 $ 0 0 $ 0  
Unrealized losses on marketable securities     $ 0   $ 0