XML 57 R47.htm IDEA: XBRL DOCUMENT v3.19.1
Income Taxes - Additional Information (Details) - USD ($)
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2018
Income Tax Disclosure [Abstract]      
Provision for income taxes $ 0 $ 0  
Unrecognized tax benefits that would impact effective tax rate $ 0   $ 0