Summary of Significant Accounting Policies - Accounts Receivable, Net (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts Receivable, Net
Allowance for doubtful accounts	$ 0	$ 100,000	$ 0
Accounts receivable written off	$ 0	$ 0	$ 0
Revenues | Customer Concentration Risk
Accounts Receivable, Net
Concentration risk percentage	98.00%	98.00%	97.00%
Revenues | Customer Concentration Risk | Customer A
Accounts Receivable, Net
Concentration risk percentage	32.00%	33.00%	30.00%
Revenues | Customer Concentration Risk | Customer B
Accounts Receivable, Net
Concentration risk percentage	32.00%	33.00%	30.00%
Revenues | Customer Concentration Risk | Customer C
Accounts Receivable, Net
Concentration risk percentage	34.00%	32.00%	37.00%
Accounts Receivable, net | Customer Concentration Risk
Accounts Receivable, Net
Concentration risk percentage	96.00%	97.00%
Accounts Receivable, net | Customer Concentration Risk | Customer A
Accounts Receivable, Net
Concentration risk percentage	45.00%	46.00%
Accounts Receivable, net | Customer Concentration Risk | Customer B
Accounts Receivable, Net
Concentration risk percentage	21.00%	24.00%
Accounts Receivable, net | Customer Concentration Risk | Customer C
Accounts Receivable, Net
Concentration risk percentage	30.00%	27.00%