We don't really have docs at this point in time, just getting the lib out of the door was quite the chunk of work; but all the things we expose follow the ISO C++ standard, and its standard library, and cppreference is a good source of documentation for that. In CUDA 10.2, we provide the contents of <cstddef>, <cstdint>, <type_traits>, and <atomic>, except in cuda::std:: instead of std::, and in <cuda/std/cstddef> and so on instead of <cstddef>. Additionally, there's cuda::atomic<T, Scope>, which provides scoped atomics; the available scopes are cuda::thread_scope_{block,device,system}. cuda::std::atomic uses cuda::thread_scope_system, and atomics only free you of data races within the specified scope.
All the things provided work both on the host and on the device, and are layout compatible, which means that you can also use them in managed memory heterogeneously between the host and the device.