Significant Customers - Concentration Risk by Risk Factor of Sales Revenue and Accounts Receivable (Details) - Customer Concentration Risk	12 Months Ended
	Dec. 31, 2019		Dec. 31, 2018
Sales Revenue, Net | Customer A
Significant customers
Concentration risk, percentage	10.70%
Accounts Receivable
Significant customers
Concentration risk, percentage	14.80%		26.30%
Accounts Receivable | Customer A
Significant customers
Concentration risk, percentage	14.80%		14.50%
Accounts Receivable | Customer B
Significant customers
Concentration risk, percentage		[1]	11.80%

[1] Accounts receivable from Customer B in 2019 did not exceed 10% of total gross accounts receivable.