In a committed ltr. she has the occasional other partner. normal?

I'm in a very committed, happy, LTR. Occasionally, she takes on another sexual partner for several weeks or months. She's very honest and forthright with details and I'm fine with it so long as she shares the experiences with me (preferably before, but certainly after) in honest and complete specifics. She's not keen on my taking another sexual partner, nor am I really interested in that either. Yes, it's arousing for me. And, yes, it absolutely is for her as well. When she shares the details with me, in fact, it almost always makes for incredible sex for both of us. In the grand scheme of things, how "normal" is this?