Summary of Significant Accounting Policies - Product Warranty (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Summary of product warranty activity
Beginning balance	$ 1,916	$ 2,074
Charges to expense	2,186	2,060
Costs incurred	(1,908)	(2,218)
Ending balance	$ 2,194	$ 1,916
Minimum
Product Liability Contingency [Line Items]
Limited product warranty period	1 year
Maximum
Product Liability Contingency [Line Items]
Limited product warranty period	2 years