Like many Google services in the Google+ era, Google Docs has undergone an interface revamp recently. If you don’t like the new standard look, you can choose from two others via a simple interface customisation.
Google Operating System notes that in addition to the default ‘Comfortable’ interface, you can also choose ‘cozy’ and ‘compact’ (which is similar to the pre-redesign interface). Click the Settings option (the cog) and make the choice under ‘Display Density’. (As ever, Google is rolling out the changes gradually so if you can’t see those options, you haven’t shifted to the new interface yet.)
Customize Google Docs Interface [Google Operating System]