v3.21.1
Summary of significant accounting policies - Basis of presentation (Details) - USD ($)
$ in Thousands
Jan. 01, 2021
Mar. 31, 2021
Dec. 31, 2020
Adoption of ASC 606      
Accumulated deficit   $ (157,944) $ (158,066)
Property and equipment, net $ 400,252 404,683 406,328
Long-term debt 198,974 199,086 171,695
Additional paid-in capital 201,947 203,900 $ 241,868
Adoption of ASC 842      
Operating lease right-of-use liabilities   $ 16,398  
Income Tax Benefit Related to Equity Component of Convertible Notes [Member]      
Adoption of ASC 606      
Tax benefit related to the equity component of the Convertible Notes that was recorded as additional paid-in capital 5,686    
Accounting Standards Update 2020-06 [Member]      
Adoption of ASC 606      
Accumulated deficit 6,566    
Gross deferred tax liabilities (27,949)    
Accounting Standards Update 2020-06 [Member] | Previously Reported [Member]      
Adoption of ASC 606      
Property and equipment, net 406,328    
Long-term debt 171,695    
Additional paid-in capital 241,868    
Accounting Standards Update 2020-06 [Member] | Adjustment for Adoption      
Adoption of ASC 606      
Property and equipment, net (6,076)    
Long-term debt 27,279    
Additional paid-in capital $ (39,921)