Restructuring charges - Narrative (Details) - USD ($) $ in Thousands			3 Months Ended		12 Months Ended
	Apr. 14, 2020	Mar. 15, 2017	Jun. 30, 2020	Mar. 31, 2018	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Restructuring Cost and Reserve [Line Items]
Restructuring charges					$ 1,226	$ 25,396	$ 1,454
Operating Lease, Impairment Loss					0	12,460	$ 0
First quarter 2017 restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Expected percent of positions eliminated		17.00%
Restructuring charges				$ 23,500
Other Restructuring Costs					384	57
First quarter 2017 restructuring [Member] | Non-cancelable Leases, Accelerated Depreciation and Other Charges [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges				13,200
First quarter 2017 restructuring [Member] | Employee Severance and Pay Related Costs [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				$ 10,300	0	0
Second quarter 2020 restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Expected percent of positions eliminated	20.00%
Restructuring charges						29,000
Other Restructuring Costs					3,347	5,800
Second quarter 2020 restructuring [Member] | Non-cancelable Leases, Accelerated Depreciation and Other Charges [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges						9,100
Second quarter 2020 restructuring [Member] | Employee Severance and Pay Related Costs [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			$ 7,400		$ 146	$ 7,287