I also agree with @polesye's concern over the use of the large and arbitrary z-index here. While I know you need to set a value that will bring these elements to the top of the UI depth-wise, I'd recommend using a smaller number and also adhere to a scale that others can understand. 

We happen to have Sass placeholders elsewhere that adhere to a depth scale (see https://github.com/edx/edx-platform/blob/master/lms/static/sass/base/_mixins.scss#L93). Since you're writing CSS and not Sass, I'd recommend just borrowing the appropriate z-index value (e.g. ```z-index: 1000;```) from that scale. Ideally, we want to not use the largest value as other UI elements may need to take front stage (such as modal windows, prompts, warnings, etc.).