They are pretty hearty plants, and separating them at just about any time of the season is usually well tolerated with them. Give some to your friends if you like. They will probably multiply well over the summer for you after thinning them out. Hope this helps, happy gardening.
I just transplanted mine 2 weeks ago. Very Easy! Dig it up and you will find many bulbs depending on how big it is. You can split it up or just replant it as is. Dig a hole and plant it. Make sure it gets watered. It is very hard to kill these plants. Good Luck.