1
general::
Also, cover the territory or waterfront. Be comprehensive. For example, The review course will cover the field very well, or Bob's new assignment really covers the territory, or The superintendent's speech covered the waterfront on the drug problem. These expressions all employ the verb cover in the sense of "extend over" or "include," a usage dating from the late 1700s, with the nouns (field, ground, territory, waterfront) each meaning "whole area."
American Heritage Idioms