Well the chord progression for D major is D, Em, F#min, G, A, Bmin, C# dim, and the relative minor is B. The resting tone built out of the chords and the progression makes it likely to be in D major opposed to B minor. Hotel California is in B minor, and your progression is distinctly different from it so I'm pretty sure it's D major.
The way to determine a key is figuring out what notes make up the scale. For D it's DEF#GABC#, and Bm is BC#DEF#GA. They have the same notes but they are tonally spelled differently. The trick for figuring out what chords fit in a major key is remembering how major keys are spelled. Chords in major progressions are Major minor minor Major Major minor diminished (I think).
Basically what I do is listen for resting tone which is usually the first or fourth chord in a progression to determine the possible major key and its relative minor. Then I listen to the structure of the song to determine the pattern and see if it fits a major or minor pattern to make logical sense (I listen for I IV V I progressions and such). Yours just makes sense in D.
You diviate from D when you throw in that C and A minor because the half step gets out of whack, but it makes for a tonally interesting transition that sounds good, and it kinda "pops" out to the listener. It would be a good place, if you have lyrics, to put something you find important or catchy because of the key change. It's guaranteed to catch attention.