---
schema_version: "secwatch.filing_event.v1"
accession: "0001628280-26-001102"
form_type: "8-K"
ticker: "WTM"
cik: "0000776867"
company_name: "WHITE MOUNTAINS INSURANCE GROUP LTD"
filed_at: "2026-01-07T23:59:59+00:00"
generated_at: "2026-05-16T11:28:24.146507+00:00"
event_type: "other_material"
sentiment: "neutral"
materiality_score: 0.35
calibrated_materiality_score: 0.35
confidence: "high"
source: SEC EDGAR
---

# Ark Insurance renews Outrigger sidecar with $70M third-party capital for 2026

## Summary
- Outrigger Re Ltd. renewed for 2026 on similar terms as 2025; deployed $70M total investor capital from third-party investors.
- Capital reduction driven by Ark's increased use of traditional quota share reinsurance for 2026.
- The sidecar provides collateralized reinsurance on a portion of Ark Bermuda's global property catastrophe portfolio.

## SEC filing metadata
- accession: 0001628280-26-001102
- form_type: 8-K
- ticker: WTM
- cik: 0000776867
- company_name: WHITE MOUNTAINS INSURANCE GROUP LTD
- filed_at: 2026-01-07T23:59:59+00:00
- event_type: other_material
- sentiment: neutral
- materiality_score: 0.35
- calibrated_materiality_score: 0.35
- confidence: high
- sec_items: 8.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/776867/000162828026001102/0001628280-26-001102-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/776867/000162828026001102/wtm-20260107.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001628280-26-001102
- JSON: https://secwatch.observer/filing/0001628280-26-001102.json
- Plain text: https://secwatch.observer/filing/0001628280-26-001102.txt

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.