| Cash and equivalents | $m | not reported | not reported | not reported | not reported | not reported | not reported | 5.9Cash and equivalents, period not labelled, at 2024-12-31$5.9m. XBRL concept us-gaap:CashAndCashEquivalentsAtCarryingValue. 10-K filed 2026-03-27, accession 0001437749-26-010078.Report this figure | not reported | not reported | 4.5Cash and equivalents, period not labelled, at 2025-12-31$4.5m. XBRL concept us-gaap:CashAndCashEquivalentsAtCarryingValue. 10-Q filed 2026-08-13, accession 0001437749-26-027458.Report this figure | 4.0Cash and equivalents, period not labelled, at 2026-03-31$4.0m. XBRL concept us-gaap:CashAndCashEquivalentsAtCarryingValue. 10-Q filed 2026-05-13, accession 0001437749-26-016537.Report this figure | 3.8Cash and equivalents, period not labelled, at 2026-06-30$3.8m. XBRL concept us-gaap:CashAndCashEquivalentsAtCarryingValue. 10-Q filed 2026-08-13, accession 0001437749-26-027458.Report this figure |
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| Total assets | $m | not reported | not reported | not reported | not reported | not reported | not reported | 56.7Total assets, period not labelled, at 2024-12-31$56.7m. XBRL concept us-gaap:Assets. 10-K filed 2026-03-27, accession 0001437749-26-010078.Report this figure | not reported | not reported | 58.7Total assets, period not labelled, at 2025-12-31$58.7m. XBRL concept us-gaap:Assets. 10-Q filed 2026-08-13, accession 0001437749-26-027458.Report this figure | 58.1Total assets, period not labelled, at 2026-03-31$58.1m. XBRL concept us-gaap:Assets. 10-Q filed 2026-05-13, accession 0001437749-26-016537.Report this figure | 57.9Total assets, period not labelled, at 2026-06-30$57.9m. XBRL concept us-gaap:Assets. 10-Q filed 2026-08-13, accession 0001437749-26-027458.Report this figure |
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| Total liabilities | $m | not reported | not reported | not reported | not reported | not reported | not reported | 26.1Total liabilities, period not labelled, at 2024-12-31$26.1m. XBRL concept us-gaap:Liabilities. 10-K filed 2026-03-27, accession 0001437749-26-010078.Report this figure | not reported | not reported | 32.8Total liabilities, period not labelled, at 2025-12-31$32.8m. XBRL concept us-gaap:Liabilities. 10-Q filed 2026-08-13, accession 0001437749-26-027458.Report this figure | 32.2Total liabilities, period not labelled, at 2026-03-31$32.2m. XBRL concept us-gaap:Liabilities. 10-Q filed 2026-05-13, accession 0001437749-26-016537.Report this figure | 30.9Total liabilities, period not labelled, at 2026-06-30$30.9m. XBRL concept us-gaap:Liabilities. 10-Q filed 2026-08-13, accession 0001437749-26-027458.Report this figure |
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| Long-term debt | $m | 9.6Long-term debt, period not labelled, at 2023-06-30$9.6m. XBRL concept us-gaap:LongTermDebt. 10-Q filed 2023-08-09, accession 0001437749-23-022831.Report this figure | 9.6Long-term debt, period not labelled, at 2023-09-30$9.6m. XBRL concept us-gaap:LongTermDebt. 10-Q filed 2023-11-14, accession 0001437749-23-031778.Report this figure | 11.0Long-term debt, period not labelled, at 2023-12-31$11.0m. XBRL concept us-gaap:LongTermDebt. 10-K filed 2024-03-29, accession 0001437749-24-009908.Report this figure | 11.4Long-term debt, period not labelled, at 2024-03-31$11.4m. XBRL concept us-gaap:LongTermDebt. 10-Q filed 2024-05-10, accession 0001437749-24-015876.Report this figure | 11.3Long-term debt, period not labelled, at 2024-06-30$11.3m. XBRL concept us-gaap:LongTermDebt. 10-Q filed 2024-08-09, accession 0001437749-24-025738.Report this figure | 11.2Long-term debt, period not labelled, at 2024-09-30$11.2m. XBRL concept us-gaap:LongTermDebt. 10-Q filed 2024-11-19, accession 0001437749-24-035730.Report this figure | 11.2Long-term debt, period not labelled, at 2024-12-31$11.2m. XBRL concept us-gaap:LongTermDebt. 10-K filed 2025-03-28, accession 0001437749-25-009691.Report this figure | 11.1Long-term debt, period not labelled, at 2025-03-31$11.1m. XBRL concept us-gaap:LongTermDebt. 10-Q filed 2025-05-05, accession 0001437749-25-014377.Report this figure | 10.9Long-term debt, period not labelled, at 2025-06-30$10.9m. XBRL concept us-gaap:LongTermDebt. 10-Q filed 2025-11-10, accession 0001437749-25-034094.Report this figure | 10.9Long-term debt, period not labelled, at 2025-12-31$10.9m. XBRL concept us-gaap:LongTermDebt. 10-K filed 2026-03-27, accession 0001437749-26-010078.Report this figure | 10.8Long-term debt, period not labelled, at 2026-03-31$10.8m. XBRL concept us-gaap:LongTermDebt. 10-Q filed 2026-05-13, accession 0001437749-26-016537.Report this figure | 10.7Long-term debt, period not labelled, at 2026-06-30$10.7m. XBRL concept us-gaap:LongTermDebt. 10-Q filed 2026-08-13, accession 0001437749-26-027458.Report this figure |
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| Shareholders' equity | $m | not reported | not reported | not reported | not reported | not reported | not reported | not reported | not reported | not reported | not reported | not reported | not reported |
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