offhand

be offhand with sb.

you were a bit offhand with her this afternoon.

I can't tell offhand how much it will cost.

He answered in such an offhand manner that I wondered if he’d misheard me.

an offhand remark. What isunrehearsed is said or done without rehearsal or practice though not necessarily without forethought:

Trust is as difficult a coin to earn and it is easily lost - the trust built over a decade can be shattered in an instant by one offhanded remark or deed.