Do you want a keyboard or software? What is your budget? Atmosphere or Omnisphere will give you all of the sounds you need. A single keyboard might be tricky to find to create intricate backing beds like are in that song.
The synth chords are a synth choir pad sound. The background sounds could sorta be made with Spectrasonics Atmosphere or Omnisphere. http://www.spectrasonics.net/products/omnisphere.php