The 105 is designed to work with a double or a triple. However, it does come with a disclaimer,(paraphrasing) "If you overstretch the shifter when used on a double, the shifter will easily break." They include a graphic showing point A to B to C, for a triple and point A to B to C for a double with the distance from B to C indicated as where the overstretch can occur.

Unfortunately, I did not know this when I put 105s on my winter bike which has a compact on it. The left shifter broke twice with less than 500 miles each time. Shimano did replace the shifter both times. However, I did got the tag with the disclaimer until the second replacement. My LBS swapped the left shifter for a new Ultegra installed for $30. To be fair, my LBS did tell me they have had no trouble with 105s and sell about 50% 105 bikes with doubles. However, from my experience, I would not put 105s on a double. My next build will be SRAM.