Supplemental balance sheet and cash flow information (other) (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Prepaid product discounts [Roll Forward]
Balance, beginning of year		$ 50,602	$ 51,145
Additions	[1]	24,284	13,259
Amortization		(23,425)	(21,725)
Other		(191)	(1,430)
Balance, end of period		51,270	41,249
Prepaid product discount payments		27,049	24,947
Accrued liabilities
Deferred revenue	[2]	43,081		$ 42,104
Employee cash bonuses, including sales incentives		35,341		21,090
Operating lease liabilities (Note 13)		12,884		11,589
Prepaid product discounts due within one year		11,805		14,365
Customer rebates		8,715		8,179
Other		91,958		79,856
Accrued liabilities		203,784		177,183
Deferred revenue recognized		33,088
Supplemental cash flow information
Cash and cash equivalents		121,064	310,430	123,122
Total cash, cash equivalents, restricted cash and restricted cash equivalents		253,104	400,016	229,409	$ 174,811
Funds held for customers [Member]
Supplemental cash flow information
Restricted cash and restricted cash equivalents included in funds held for customers		129,180	$ 89,586
Other non-current assets [Member]
Supplemental cash flow information
Non-current restricted cash included in other non-current assets		$ 2,860		$ 0

[1] Prepaid product discounts are generally accrued upon contract execution. Cash payments for prepaid product discounts were $27,049 for the nine months ended September 30, 2021 and $24,947 for the nine months ended September 30, 2020.

[2] $33,088 of the December 31, 2020 amount was recognized as revenue during the nine months ended September 30, 2021.