a transparent (virtually literal) idiom

an opaque binomial

a literal trinomial

an opaque idiom

a figurative idiom whose meaning can be surmised

a semi-opaque trinomial

mad, bad and dangerous to know

she waited till he kicked the bucket

they are as different as chalk and cheese

now you are a small fish in a big pond rather than a big fish in a small pond

he ummed and ahed

blood, sweat and tears