Defined contribution and defined benefit retirement plans - Composition of Pension Plan Assets (Details) - Pension Plans - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Defined benefit pension plans [Line Items]
Plan assets	$ 464.9	$ 480.6
Quoted prices in active markets (Level 1)
Defined benefit pension plans [Line Items]
Plan assets	113.4	138.6
Significant other observable input (Level 2)
Defined benefit pension plans [Line Items]
Plan assets	21.0	17.4
Significant unobservable inputs (Level 3)
Defined benefit pension plans [Line Items]
Plan assets	329.5	286.0	$ 292.1
Assets measured at NAV
Defined benefit pension plans [Line Items]
Plan assets	1.0	38.6
Non-U.S.
Defined benefit pension plans [Line Items]
Plan assets	$ 455.9	$ 404.9	$ 422.6
Long-term return on plan assets	4.50%	4.90%	4.60%
GERMANY
Defined benefit pension plans [Line Items]
Plan assets	$ 304.9	$ 264.6
GERMANY | Significant unobservable inputs (Level 3)
Defined benefit pension plans [Line Items]
Plan assets	304.9	264.6
CANADA | Local Currency Equities
Defined benefit pension plans [Line Items]
Plan assets	2.5	2.8
CANADA | Local Currency Fixed Income
Defined benefit pension plans [Line Items]
Plan assets	79.1	78.1
CANADA | Cash and other
Defined benefit pension plans [Line Items]
Plan assets	0.1	0.5
CANADA | Quoted prices in active markets (Level 1) | Local Currency Equities
Defined benefit pension plans [Line Items]
Plan assets	2.5	2.8
CANADA | Quoted prices in active markets (Level 1) | Local Currency Fixed Income
Defined benefit pension plans [Line Items]
Plan assets	79.1	78.1
CANADA | Quoted prices in active markets (Level 1) | Cash and other
Defined benefit pension plans [Line Items]
Plan assets	0.1	0.5
NORWAY | Local Currency Equities
Defined benefit pension plans [Line Items]
Plan assets	2.3	2.0
NORWAY | Non Local Currency Equities
Defined benefit pension plans [Line Items]
Plan assets	7.5	6.9
NORWAY | Local Currency Fixed Income
Defined benefit pension plans [Line Items]
Plan assets	25.7	21.1
NORWAY | Non Local Currency Fixed Income
Defined benefit pension plans [Line Items]
Plan assets	4.8	4.2
NORWAY | Cash and other
Defined benefit pension plans [Line Items]
Plan assets	4.5	3.6
NORWAY | Real Estate
Defined benefit pension plans [Line Items]
Plan assets	$ 7.4	6.2
Long-term return on plan assets	7.00%
NORWAY | Fixed Income
Defined benefit pension plans [Line Items]
Long-term return on plan assets	5.00%
NORWAY | Quoted prices in active markets (Level 1) | Local Currency Equities
Defined benefit pension plans [Line Items]
Plan assets	$ 2.3	2.0
NORWAY | Quoted prices in active markets (Level 1) | Non Local Currency Equities
Defined benefit pension plans [Line Items]
Plan assets	7.5	6.9
NORWAY | Quoted prices in active markets (Level 1) | Local Currency Fixed Income
Defined benefit pension plans [Line Items]
Plan assets	4.7	3.7
NORWAY | Quoted prices in active markets (Level 1) | Non Local Currency Fixed Income
Defined benefit pension plans [Line Items]
Plan assets	4.8	4.2
NORWAY | Quoted prices in active markets (Level 1) | Cash and other
Defined benefit pension plans [Line Items]
Plan assets	4.4	3.4
NORWAY | Significant other observable input (Level 2) | Local Currency Fixed Income
Defined benefit pension plans [Line Items]
Plan assets	$ 21.0	17.4
NORWAY | Significant unobservable inputs (Level 3)
Defined benefit pension plans [Line Items]
Percentage of plan asset allocation	14.00%
NORWAY | Significant unobservable inputs (Level 3) | Cash and other
Defined benefit pension plans [Line Items]
Plan assets	$ 0.1	0.2
NORWAY | Significant unobservable inputs (Level 3) | Real Estate
Defined benefit pension plans [Line Items]
Plan assets	7.4	6.2
Other.
Defined benefit pension plans [Line Items]
Plan assets	17.1	14.9
Other. | Significant unobservable inputs (Level 3)
Defined benefit pension plans [Line Items]
Plan assets	17.1	14.9
UNITED STATES
Defined benefit pension plans [Line Items]
Plan assets	$ 9.0	$ 75.7	$ 40.3
Long-term return on plan assets	5.00%	5.00%	5.00%
UNITED STATES | Cash and other
Defined benefit pension plans [Line Items]
Plan assets	$ 9.0	$ 38.2
UNITED STATES | Equities
Defined benefit pension plans [Line Items]
Plan assets		6.7
UNITED STATES | Fixed Income
Defined benefit pension plans [Line Items]
Plan assets		30.8
UNITED STATES | Quoted prices in active markets (Level 1) | Cash and other
Defined benefit pension plans [Line Items]
Plan assets	8.0	37.0
UNITED STATES | Significant unobservable inputs (Level 3) | Equities
Defined benefit pension plans [Line Items]
Plan assets		0.1
UNITED STATES | Assets measured at NAV | Cash and other
Defined benefit pension plans [Line Items]
Plan assets	$ 1.0	1.2
UNITED STATES | Assets measured at NAV | Equities
Defined benefit pension plans [Line Items]
Plan assets		6.6
UNITED STATES | Assets measured at NAV | Fixed Income
Defined benefit pension plans [Line Items]
Plan assets		$ 30.8