cmake.css has: /* Import the Sphinx theme style. */ @import url("default.css"); But no such file is installed. As a result, all docs are style-less.
$ qlist cmake | grep css /usr/share/doc/cmake-3.2.1/html/_static/cmake.css /usr/share/doc/cmake-3.2.1/html/_static/default.css /usr/share/doc/cmake-3.2.1/html/_static/basic.css /usr/share/doc/cmake-3.2.1/html/_static/pygments.css