Your butterfly is probably from the family Lycaenidae and the subfamily Polyommatinae; also known as the Blues. They get their name because the upperside has some tint of blue. Females will tend be more drab with bluish tint while males can be very bright blue (the pictures of females that we have do not show the bluish tint clearly). Below are a few of the representative species known to occur in Idaho.
Does your butterfly look like this?