Fitch Ratings has downgraded White Mountains Insurance Group Ltd.'s issuer default rating to BBB from BBB+.

The ratings outlook is evolving.

Fitch's rationale for the downgrade of White Mountains coincides with the application of Fitch's bespoke criteria for White Mountains following the merger of OneBeacon Insurance Group Ltd. into Intact Financial Corp.

Fitch said the transaction alters White Mountains' credit profile. The rating agency constrains White Mountains' issuer default rating to account for the significant uncertainty regarding long-term strategy.

Fitch estimates Sept. 30 financial leverage to be less than 1%, total financing and commitments ratio of less than 0.1x, and risky assets to equity of approximately 24%. White Mountains' ratings will be evaluated following capital deployment and the company's go forward strategy, the agency said.