Nature of operations and presentation of financial statements - immaterial error (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Information by reportable segment
Net sales	$ 1,785.6	$ 1,519.0
Provision for accounts receivable and inventory	7.9	16.6
Inventory	(54.3)	2.3
Proprietary materials & consumables
Information by reportable segment
Net sales	565.2	478.5
Third party materials & consumables
Information by reportable segment
Net sales	758.4	650.4
Services & specialty procurement
Information by reportable segment
Net sales	219.8	191.1
Equipment & instrumentation
Information by reportable segment
Net sales	$ 242.2	199.0
Previously Reported
Information by reportable segment
Net sales		1,519.0
Provision for accounts receivable and inventory		13.6
Inventory		5.3
Previously Reported | Proprietary materials & consumables
Information by reportable segment
Net sales		533.1
Previously Reported | Third party materials & consumables
Information by reportable segment
Net sales		604.6
Previously Reported | Services & specialty procurement
Information by reportable segment
Net sales		178.0
Previously Reported | Equipment & instrumentation
Information by reportable segment
Net sales		203.3
Adjustment
Information by reportable segment
Net sales		0.0
Provision for accounts receivable and inventory		3.0
Inventory		3.0
Adjustment | Proprietary materials & consumables
Information by reportable segment
Net sales		(54.6)
Adjustment | Third party materials & consumables
Information by reportable segment
Net sales		45.8
Adjustment | Services & specialty procurement
Information by reportable segment
Net sales		13.1
Adjustment | Equipment & instrumentation
Information by reportable segment
Net sales		$ (4.3)