Arch MI benefits from its strong penetration in the niche credit-union mortgage insurance channel. We are affirming our ratings on Arch MI and revising the outlook to positive from stable. The positive outlook reflects the possibility of Arch MI becoming strategically important to the group. NEW YORK (Standard&Poor's) Nov. 21, 2014--Standard&Poor's Ratings Services said today that it revised its outlook on Arch Mortgage Insurance Co. (Arch MI) to positive from stable. At the same time, we affirmed our 'BBB+' financial strength and long-term counterparty credit ratings on the company. In our view Arch MI is an important component of Arch Capital Group Ltd.'s (Arch) broader strategy of diversifying into the mortgage (re)insurance space, toward which the