Annual report pursuant to Section 13 and 15(d)

Concentrations (Details)

v3.10.0.1
Concentrations (Details) - leased_property
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Concentration Risk [Line Items]      
Number of significant leased properties 2    
Revenue from Contract with Customer | Customer Concentration Risk      
Concentration Risk [Line Items]      
Percentage of revenues 6.00% 11.00% 12.00%