Debt and Other Obligations - Schedule of Other Short-Term Debt and Obligations (Details) $ in Millions	Jun. 30, 2026 USD ($)	Jun. 30, 2026 EUR (€)	Dec. 31, 2025 USD ($)	Dec. 31, 2025 EUR (€)
Debt Instrument [Line Items]
Repurchase Agreement	$ 48.9		$ 43.0
Total of Other Short-term Debt and Obligations	342.6		289.8
Revolving Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Outstanding	125.3		58.8
Borrowing capacity	398.8	€ 350,000,000
Revolving Credit Facility | Ancillary Credit Facilities
Debt Instrument [Line Items]
Borrowing capacity	266.6	€ 234,000,000.0	275.0	€ 234,000,000.0
Revolving Credit Facility | OEC GmbH outstanding borrowings | Ancillary Credit Facilities
Debt Instrument [Line Items]
Outstanding	127.1		127.9
Revolving Credit Facility | OEC LLC outstanding borrowings | Ancillary Credit Facilities
Debt Instrument [Line Items]
Outstanding	12.5		19.4
Revolving Credit Facility | OEC Huaibei outstanding borrowings | Ancillary Credit Facilities
Debt Instrument [Line Items]
Outstanding	0.0		4.6
Working Capital Loans | Korea Working Capital Loans (capacity $46.7 million)
Debt Instrument [Line Items]
Borrowing capacity	46.7
Working Capital Loans | Korea Working Capital Loans (capacity $46.7 million) | Uncommitted
Debt Instrument [Line Items]
Outstanding	1.6		1.7
Working Capital Loans | Korea Working Capital Loans (capacity $46.7 million) | Committed
Debt Instrument [Line Items]
Outstanding	12.9		17.3
Working Capital Loans | China Working Capital Loans (capacity $18.0 million) | China Working Capital Loans (capacity $18.0 million)
Debt Instrument [Line Items]
Outstanding	14.3		$ 17.1
Borrowing capacity	$ 18.0