It is up to the umbrella carrier. I was given a quote for an umbrella from Company B (large ubiquitous carrier) when I had a vehicle insured by Company A. They wanted to see Company A's policy and Company B's quote was contingent on raising the liability limits. Just to simplify things I changed all the policies to Company B.
I have a $2M Geico umbrella @ $333/yr. For having no high risk toys/activities (I have not been employed as a professional athlete in the last 10 years. That was one of the questions ), maybe that rate is a little high, but I just recently insured my cars (including a new 2015 purchase) through Geico for substantially less than what any other company quoted. So, it's all good. Well... it's all INSURANCE... However you may feel about that.
Homeowners is through MetLife.