Related party disclosures - Summary of Total Compensation of Key Management Personnel (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Compensation of key management personnel [abstract]
Short-term employment benefits	$ 10.5	$ 15.8	$ 18.2
Contributions to defined contribution pension plans	0.3	0.5	0.5
Equity compensation benefits	2.3	12.1	13.0
Total compensation of key management personnel	$ 13.1	$ 28.4	$ 31.7

The amount of compensation to key management personnel. [Refer: Key management personnel of entity or parent [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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The amount of compensation to key management personnel in the form of post-employment benefits. [Refer: Key management personnel of entity or parent [member]]

+ References

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The amount of compensation to key management personnel in the form of share-based payments. [Refer: Key management personnel of entity or parent [member]]

+ References

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The amount of compensation to key management personnel in the form of short-term employee benefits. [Refer: Key management personnel of entity or parent [member]]

+ References

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Compensation of key management personnel abstract.

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