Derivatives and Fair Value Measurements - Derivatives by Balance Sheet Classification (Details) $ in Millions	Dec. 31, 2021 AUD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Designated as Hedging Instrument
Asset Derivative
Asset derivatives, gross		$ 64.3	$ 27.4
Effect of counterparty netting, derivative assets		(59.5)	(16.2)
Variation margin (held) posted on derivative assets		(3.4)	(0.3)
Net derivative assets and margin as classified in the balance sheets		1.4	10.9
Liability Derivative
Liability derivatives, gross		(184.2)	(24.7)
Effect of counterparty netting, derivative liabilities		59.5	16.2
Variation margin (held) posted on derivative liabilities		95.2	6.8
Net derivative liabilities and margin as classified in the balance sheets		(29.5)	(1.7)
Foreign currency option contracts
Liability Derivative
Derivative, Notional Amount	$ 535,000,000
Foreign currency option contracts | Designated as Hedging Instrument
Asset Derivative
Asset derivatives, gross		1.4	10.3
Liability Derivative
Liability derivatives, gross		0.0	0.0
Derivative contracts related to forecasted sales | Designated as Hedging Instrument
Asset Derivative
Asset derivatives, gross		59.5	16.7
Liability Derivative
Liability derivatives, gross		(184.2)	(24.7)
Financial trading contracts | Designated as Hedging Instrument
Asset Derivative
Asset derivatives, gross		3.4	0.4
Liability Derivative
Liability derivatives, gross		$ 0.0	$ 0.0