Significant Accounting Policies - Property, Plant and Equipment (Details)	12 Months Ended
	Dec. 31, 2020
Operating equipment | Minimum
Property, Plant and Equipment
Useful lives (in years)	3 years
Operating equipment | Maximum
Property, Plant and Equipment
Useful lives (in years)	20 years
Building and leasehold improvements | Minimum
Property, Plant and Equipment
Useful lives (in years)	15 years
Building and leasehold improvements | Maximum
Property, Plant and Equipment
Useful lives (in years)	39 years
Furniture and fixtures | Minimum
Property, Plant and Equipment
Useful lives (in years)	5 years
Furniture and fixtures | Maximum
Property, Plant and Equipment
Useful lives (in years)	7 years
Computer software
Property, Plant and Equipment
Useful lives (in years)	5 years
Vehicles | Minimum
Property, Plant and Equipment
Useful lives (in years)	3 years
Vehicles | Maximum
Property, Plant and Equipment
Useful lives (in years)	5 years