XML 58 R39.htm IDEA: XBRL DOCUMENT v3.19.3.a.u2
Summary of Significant Accounting Policies - Narrative (Details) - USD ($)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Accounting Policies [Abstract]      
Asset impairment charges $ 0 $ 0 $ 0