First, you need to make sure your table is 100% wide, then you can do the same with th and td
table, td { width: 100%; }
EDIT: since you edited your original post, you should give the first td class
<td class="first"> td.first { width: 100%; }
This will cause the first column to use as much of the page as possible, and the second column will be wide enough for the content. You may need to give it a width as well if you do not want your text to be wrapped or something else.
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