US-based insurer Ironshore has filed plans for an initial public offering of its shares, enabling the founders to sell down their holdings.

The company – which bought local insurer Assetinsure in February – was formed in 2006 as a specialist property and casualty insurer with more than $1 billion in private equity capital. 

It has filed documents for a $US100 million ($107 million) capital-raising, a figure given to satisfy listing requirements.

No pricing details have been given for the shares, so the offer could raise more.

The company is majority owned by six private equity firms. The initial filing with the US Securities and Exchange Commission does not detail their shareholdings post-listing.