Concentrations of risk and geographic information - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Revenue, Major Customer [Line Items]
Revenue	$ 249,586,000	$ 134,246,000	$ 453,266,000	$ 253,646,000
United States [Member]
Revenue, Major Customer [Line Items]
Revenue	131,400,000	$ 76,800,000	224,700,000	$ 122,500,000
Outside the United States [Member]
Revenue, Major Customer [Line Items]
Long-lived assets	$ 5,800,000		$ 5,800,000		$ 6,900,000