Defined contribution and defined benefit retirement plans - Composition of Pension Plan Assets (Detail) - Defined benefit pension plans - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	$ 435.1	$ 395.6
Foreign Pension Plans Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	422.6	383.6	$ 470.1
D E
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	269.4	234.0
Other.
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	15.9	17.3
U S
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	12.5	12.0	$ 15.9
Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	111.2	111.1
Level 1 | Other.
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		0.4
Level 2
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	19.5	14.8
Level 3
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	292.1	259.0
Level 3 | D E
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	269.4	234.0
Level 3 | Other.
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	15.9	16.9
Assets Measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	12.3	10.7
Local currency equities | C A
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		0.1
Local currency equities | N O
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	2.4	2.3
Local currency equities | Level 1 | C A
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		0.1
Local currency equities | Level 1 | N O
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	2.4	2.3
Non local currency equities | C A
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	2.7	11.0
Non local currency equities | N O
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	7.2	4.7
Non local currency equities | Level 1 | C A
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	2.7	11.0
Non local currency equities | Level 1 | N O
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	7.2	4.7
Local currency fixed income | C A
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	86.2	72.9
Local currency fixed income | N O
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	23.9	21.8
Local currency fixed income | Level 1 | C A
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	86.2	72.9
Local currency fixed income | Level 1 | N O
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	4.4	7.0
Local currency fixed income | Level 2 | N O
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	19.5	14.8
Cash and other | C A
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1.1	0.6
Cash and other | N O
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	3.0	2.7
Cash and other | U S
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0.6	1.2
Cash and other | Level 1 | C A
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1.1	0.6
Cash and other | Level 1 | N O
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	2.8	2.4
Cash and other | Level 1 | U S
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0.2	0.9
Cash and other | Level 3 | N O
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0.2	0.3
Cash and other | Assets Measured at NAV | U S
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0.4	0.3
Non local currency fixed income | N O
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	4.2	8.4
Non local currency fixed income | Level 1 | N O
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	4.2	8.4
Real estate | N O
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	6.6	7.8
Real estate | Level 3 | N O
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	6.6	7.8
Equity | U S
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	3.5	3.8
Equity | Level 1 | U S
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		0.3
Equity | Assets Measured at NAV | U S
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	3.5	3.5
Fixed Income | U S
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	8.4	7.0
Fixed Income | Level 1 | U S
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		0.1
Fixed Income | Assets Measured at NAV | U S
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	$ 8.4	$ 6.9