Fair Value Measurements - Recurring Measurements (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Derivative assets:
Derivative assets	$ 11.9	$ 5.7
Derivative liabilities:
Total derivative liabilities	(11.9)	(5.7)
Fair Value, Measurements, Recurring
Derivative assets:
Derivative assets	11.9	5.7
Pension plan investments	26.3	25.9
Total recurring assets at fair value	38.2	31.6
Derivative liabilities:
Total derivative liabilities	0.0	0.0
Precious metals obligations	0.0	(5.2)
Liability awards	(32.4)	(67.8)
Total recurring liabilities at fair value	(32.4)	(73.0)
Fair Value, Measurements, Recurring | Inventory financing obligation
Derivative liabilities:
Total derivative liabilities	0.0	0.0
Fair Value, Measurements, Recurring | Inventory financing obligation
Derivative assets:
Derivative assets	11.9	5.7
Fair Value, Measurements, Recurring | Level 1
Derivative assets:
Derivative assets	0.0	0.0
Pension plan investments	3.7	3.7
Total recurring assets at fair value	3.7	3.7
Derivative liabilities:
Total derivative liabilities	0.0	0.0
Precious metals obligations	0.0	(5.2)
Liability awards	(32.4)	(67.8)
Total recurring liabilities at fair value	(32.4)	(73.0)
Fair Value, Measurements, Recurring | Level 1 | Inventory financing obligation
Derivative liabilities:
Total derivative liabilities	0.0	0.0
Fair Value, Measurements, Recurring | Level 1 | Inventory financing obligation
Derivative assets:
Derivative assets	0.0	0.0
Fair Value, Measurements, Recurring | Level 2
Derivative assets:
Derivative assets	0.0	0.0
Pension plan investments	22.6	22.2
Total recurring assets at fair value	22.6	22.2
Derivative liabilities:
Total derivative liabilities	0.0	0.0
Precious metals obligations	0.0	0.0
Liability awards	0.0	0.0
Total recurring liabilities at fair value	0.0	0.0
Fair Value, Measurements, Recurring | Level 2 | Inventory financing obligation
Derivative liabilities:
Total derivative liabilities	0.0	0.0
Fair Value, Measurements, Recurring | Level 2 | Inventory financing obligation
Derivative assets:
Derivative assets	0.0	0.0
Fair Value, Measurements, Recurring | Level 3
Derivative assets:
Derivative assets	11.9	5.7
Pension plan investments	0.0	0.0
Total recurring assets at fair value	11.9	5.7
Derivative liabilities:
Total derivative liabilities	0.0	0.0
Precious metals obligations	0.0	0.0
Liability awards	0.0	0.0
Total recurring liabilities at fair value	0.0	0.0
Fair Value, Measurements, Recurring | Level 3 | Inventory financing obligation
Derivative liabilities:
Total derivative liabilities	0.0	0.0
Fair Value, Measurements, Recurring | Level 3 | Inventory financing obligation
Derivative assets:
Derivative assets	$ 11.9	$ 5.7