Segment Information, Geographic and Product Data - Summarized Financial Information by Segment (Details) - USD ($) |
3 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Jun. 30, 2026 |
Mar. 31, 2026 |
Dec. 31, 2025 |
Sep. 30, 2025 |
Jun. 30, 2025 |
Mar. 31, 2025 |
Dec. 31, 2024 |
Sep. 30, 2024 |
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2024 |
|
| Segment Reporting [Line Items] | |||||||||||
| Consolidated net sales | $ 851,000,000.0 | $ 811,500,000 | $ 728,000,000.0 | $ 733,700,000 | $ 755,600,000 | $ 727,000,000.0 | $ 676,900,000 | $ 717,600,000 | $ 3,124,200,000 | $ 2,877,100,000 | $ 2,759,700,000 |
| Cost of sales | 2,168,700,000 | 2,108,500,000 | 2,175,400,000 | ||||||||
| Operating income | $ 206,900,000 | $ 186,500,000 | $ 155,200,000 | $ 153,300,000 | $ 151,400,000 | $ 137,800,000 | $ 118,900,000 | $ 113,600,000 | 702,000,000.0 | 521,800,000 | 323,100,000 |
| Interest expense, net | 37,800,000 | 48,400,000 | 51,000,000.0 | ||||||||
| Debt extinguishment losses | 15,600,000 | 0 | 0 | ||||||||
| Other (income) expense, net | (7,600,000) | 6,100,000 | 60,500,000 | ||||||||
| Income before income taxes | 656,200,000 | 467,300,000 | 211,600,000 | ||||||||
| Intersegment | |||||||||||
| Segment Reporting [Line Items] | |||||||||||
| Consolidated net sales | (85,600,000) | (91,900,000) | (95,100,000) | ||||||||
| Operating income | (2,300,000) | (900,000) | 1,600,000 | ||||||||
| Operating | |||||||||||
| Segment Reporting [Line Items] | |||||||||||
| Consolidated net sales | 3,209,800,000 | 2,969,000,000 | 2,854,800,000 | ||||||||
| Cost of sales | 2,252,600,000 | 2,199,800,000 | 2,272,500,000 | ||||||||
| Other segment items | 144,200,000 | 143,600,000 | 137,800,000 | ||||||||
| Operating income | 813,000,000.0 | 625,600,000 | 444,500,000 | ||||||||
| Corporate | |||||||||||
| Segment Reporting [Line Items] | |||||||||||
| Operating income | (108,700,000) | (102,900,000) | (123,000,000.0) | ||||||||
| Specialty Alloys Operations | |||||||||||
| Segment Reporting [Line Items] | |||||||||||
| Consolidated net sales | 2,811,700,000 | 2,548,700,000 | 2,432,800,000 | ||||||||
| Specialty Alloys Operations | Intersegment | |||||||||||
| Segment Reporting [Line Items] | |||||||||||
| Consolidated net sales | (15,100,000) | (14,900,000) | (11,000,000.0) | ||||||||
| Specialty Alloys Operations | Operating | |||||||||||
| Segment Reporting [Line Items] | |||||||||||
| Consolidated net sales | 2,826,800,000 | 2,563,600,000 | 2,443,800,000 | ||||||||
| Cost of sales | 1,920,700,000 | 1,855,800,000 | 1,923,000,000 | ||||||||
| Other segment items | 123,200,000 | 119,200,000 | 112,300,000 | ||||||||
| Operating income | 782,900,000 | 588,600,000 | 408,500,000 | ||||||||
| Performance Engineered Products | |||||||||||
| Segment Reporting [Line Items] | |||||||||||
| Consolidated net sales | 312,500,000 | 328,400,000 | 326,900,000 | ||||||||
| Performance Engineered Products | Intersegment | |||||||||||
| Segment Reporting [Line Items] | |||||||||||
| Consolidated net sales | (70,500,000) | (77,000,000.0) | (84,100,000) | ||||||||
| Performance Engineered Products | Operating | |||||||||||
| Segment Reporting [Line Items] | |||||||||||
| Consolidated net sales | 383,000,000.0 | 405,400,000 | 411,000,000.0 | ||||||||
| Cost of sales | 331,900,000 | 344,000,000.0 | 349,500,000 | ||||||||
| Other segment items | 21,000,000.0 | 24,400,000 | 25,500,000 | ||||||||
| Operating income | $ 30,100,000 | $ 37,000,000.0 | $ 36,000,000.0 | ||||||||