The top chart reflects the Bloomberg Politics Poll -- done between June 10th and 13th of a random national sample of 1,000 adults, with a margin of error of 3.1 points.
The second chart above reflects the NBC News Poll -- done between June 6th and 12th of 9,355 registered voters, and has a margin of error of 1.4 points.
The Bloomberg poll has Clinton with an 18 point lead over Trump. The NBC poll has Clinton with a 7 point lead over Trump. And Clinton maintains that lead even if you toss Johnson (libertarian) and Stein (Green) into the mix (see charts at bottom).
Keep in mind that these numbers are with Sanders still claiming to be a viable candidate. Once he drops out, I expect Clinton's numbers to get a nice boost.