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Share-based awards - Summary of Stock Option Activity (Details) - Employee Stock Option - $ / shares			6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Options Outstanding Number of Shares
Outstanding at beginning of period (in shares)			553,746
Granted (in shares)			100,299
Exercised (in shares)			(4,020)
Canceled/expired (in shares)			0
Outstanding at end of period (in shares)	650,025	553,746	650,025
Exercisable at end of period (in shares)	336,942		336,942
Weighted Average Exercise Price
Outstanding at beginning of period (USD per share)			$ 108.53
Granted (USD per share)			177.76
Exercised (USD per share)			42.24
Canceled/expired (USD per share)			0
Outstanding at end of period (USD per share)	$ 119.62	$ 108.53	119.62
Exercisable at end of period (USD per share)	92.71		92.71
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (USD per share)			31.63
Granted (USD per share)			49.15	$ 42.43
Exercised (USD per share)			14.07
Canceled/expired (USD per share)			0
Outstanding at end of period (USD per share)	34.44	$ 31.63	34.44
Exercisable at end of period (USD per share)	$ 27.42		$ 27.42
Weighted Average Remaining Contractual Life
Outstanding at end of period	4 years 10 months 24 days	4 years 10 months 9 days
Exercisable at end of period	3 years 7 months 17 days

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Share-based Compensation Arrangement by Share-based Payment Award, Options, Weighted Average Remaining Contractual Term [Abstract]

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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