| Segment Reporting [Table Text Block] |
| | | Three Months Ended September 30, 2026 | | | Six Months Ended September 30, 2026 | |
| | | Grid | | | Wind | | | Unallocated | | | Total | | | Grid | | | Wind | | | Unallocated | | | Total | |
| Segment operating income: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| Revenues | | $ | 76,667 | | | $ | 17,371 | | | $ | — | | | $ | 94,038 | | | $ | 152,990 | | | $ | 35,120 | | | $ | — | | | $ | 188,111 | |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| Less (a) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| Segment other operating expenses (b) | | | 76,826 | | | | 13,184 | | | | (1,332 | ) | | | 88,678 | | | | 155,315 | | | | 27,051 | | | | (9,447 | ) | | | 172,919 | |
| Segment operating income (loss) | | $ | (159 | ) | | $ | 4,187 | | | $ | 1,332 | | | $ | 5,360 | | | $ | (2,325 | ) | | $ | 8,069 | | | $ | 9,447 | | | $ | 15,191 | |
| | | Three Months Ended September 30, 2025 | | | Six Months Ended September 30, 2025 | |
| | | Grid | | | Wind | | | Unallocated | | | Total | | | Grid | | | Wind | | | Unallocated | | | Total | |
| Segment operating income: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| Revenues | | $ | 54,342 | | | $ | 11,520 | | | $ | — | | | $ | 65,862 | | | $ | 114,429 | | | $ | 23,791 | | | $ | — | | | $ | 138,220 | |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| Less (a) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| Segment other operating expenses (b) | | | 53,064 | | | | 9,833 | | | | — | | | | 62,897 | | | | 108,994 | | | | 20,616 | | | | — | | | | 129,610 | |
| Segment operating income | | $ | 1,278 | | | $ | 1,687 | | | $ | — | | | $ | 2,965 | | | $ | 5,435 | | | $ | 3,175 | | | $ | — | | | $ | 8,610 | |
| | | Three Months Ended September 30, | | | Six Months Ended September 30, | |
| | | 2026 | | | 2025 | | | 2026 | | | 2025 | |
| | | | | | | | | | | | | | | | | |
| Operating income: | | $ | 5,360 | | | $ | 2,965 | | | $ | 15,191 | | | $ | 8,610 | |
| Interest income, net | | | 1,430 | | | | 2,269 | | | | 2,967 | | | | 3,201 | |
| Other expense, net | | | (396 | ) | | | (367 | ) | | | (1,012 | ) | | | (21 | ) |
| Income before income tax expense | | $ | 6,394 | | | $ | 4,867 | | | $ | 17,146 | | | $ | 11,790 | |
| | | Three Months Ended September 30, | | | Six Months Ended September 30, | |
| | | 2026 | | | 2025 | | | 2026 | | | 2025 | |
| | | | | | | | | | | | | | | | | |
| Grid | | $ | 2,519 | | | $ | 1,266 | | | $ | 5,122 | | | $ | 2,468 | |
| Wind | | | 64 | | | | 31 | | | | 107 | | | | 57 | |
| Total | | $ | 2,583 | | | $ | 1,297 | | | $ | 5,230 | | | $ | 2,525 | |
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