I have a select with my custom data-placeholder parameter:

<select class="chosen" multiple data-placeholder="Выберите доступные колонки документа">
    <option>Колонка</option>
    <option>Колонка</option>
    <option>Колонка</option>
    <option>Колонка</option>
    <option>Колонка</option>
</select>

Initialize plugin with only width-option:

$('.chosen').chosen({ width: "100%" });

And result like this:

I take a look into dev tools, and see that for .chzn-choices li.search-field input inline style set width to 90px. That too small for long placeholder.

P.S.: jQuery Chosen 0.12.1, jQuery 1.10.1