Stock compensation plans - Share-based Compensation Activity (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Stock-based compensation	$ 22,937	$ 20,739	$ 26,940
Tax benefit from compensation expense	10,912	21,958	21,121
Net excess tax benefit from compensation expense	$ 6,355	$ 17,549	$ 15,380

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 718
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-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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