Why is goodwill recorded as an asset? If the fair market value of an acquired company is $11m and purchased for $20m, I feel like the excess $9m would be considered an expense? I don't understand where there is a value. Also, is goodwill only on the balance sheet at the end of the period it was acquired or does goodwill continually make an appearance based on the fluctuating market value of the assumed business?

Goodwill is an intangible and often arises out of the premium in an acquisition. You cannot equate goodwill to fluctuating market value but you should have a plan to write it off over time. You cannot just treat a capital item like Goodwill as an expense unless the writeoff is an extraordinary expense. How did you determine the fair market value of the company, from the share price? That is not a measure of goodwill

The old saying is if there is no goodwill there should be and it it exists it shouldn't. Fluctuations in market values of specific assets are usually dealt with in a revaluation reserve