Segment Information - Reconciliation of Assets to Consolidated (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Segment Reporting [Line Items]
Total assets	$ 5,372.0	$ 5,807.2
Seaborne Mining
Segment Reporting [Line Items]
Total assets	2,375.0	2,543.4
US Thermal Mining
Segment Reporting [Line Items]
Total assets	1,300.9	1,301.7
Corporate and Other (1)
Segment Reporting [Line Items]
Total assets	$ 1,696.1	$ 1,962.1

Amount of asset recognized for present right to economic benefit.

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+ Details

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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