Summary of Significant Accounting Policies - Revenue Recognition (Details)	12 Months Ended
	Dec. 31, 2019
Product warranty period	1 year
Systems
Payment upon delivery of parts, period	90 days
Minimum | Aftermarket
Product warranty period	1 year
Minimum | Systems
Payment upon delivery of parts, period	30 days
Maximum | Aftermarket
Product warranty period	3 years
Maximum | Systems
Payment upon delivery of parts, period	60 days