Derivative Financial Instruments - Schedule of Outstanding Copper Swap Contracts (Detail) - Copper Swap Contracts [Member] £ in Millions, $ in Millions	Mar. 31, 2020 USD ($)	Mar. 31, 2020 GBP (£)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 GBP (£)
Derivatives Fair Value [Line Items]
Copper Swap Contracts Units Outstanding | £		£ 90.2		£ 73.1
Net Fair Value - (Liability) Asset | $	$ (35.0)		$ 6.2
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Derivatives Fair Value [Line Items]
Copper Swap Contracts Units Outstanding | £		73.7		56.5
Net Fair Value - (Liability) Asset | $	(28.9)		4.5
Not Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Copper Swap Contracts Units Outstanding | £		£ 16.5		£ 16.6
Net Fair Value - (Liability) Asset | $	$ (6.1)		$ 1.7