tax on investments applicable to insurance companies

Hi all. I’m a new professional in Toronto, Canada. My company started to manage a US P&C insurance company fund, but I am not familiar with US taxation. I tried to google “US insurance company investment income tax” but failed to find useful results. I tried to go on IRS but failed to find useful info, either. Could you show me some links containing useful articles/guidance/legal documents for my purpose? Thank you very much!