A domestic mutual insurer after being authorized to transact one kind of insurance shall be authorized by the director to transact such additional kinds of insurance as are authorized under section 20-209 and upon otherwise qualifying therefor and depositing and thereafter maintaining on deposit as required through the director unimpaired surplus funds in an amount not less than the amount of minimum required capital stock required of a domestic stock insurer transacting like kinds of insurance, and subject further to the additional surplus requirements of section 20-211.