Foolish Fool

I saw this on IFC sometime ago and can't remember what it was called. I remember bits of it but not the actors (which I know they are famous but can't remember). I believe the plot revolves a woman who hires a "private detective" type of guy, who sets up a fake death for her.

When he sets up the murder, he's in the motel with her, and makes it look like a murder scene, then grabs her and takes her to the trunk of the car and looks suspicious.

Also, not sure if it was the same movie but there was a scene where this guy and the woman are on the road and he stops at a rest stop, there is a big rock that holds the door to the restroom open, and the woman picks it up and hits the guy with it.

Any help is appreciated! It's been bugging me for a while and I couldn't find the title of it. I feel like it's an easy one but something blocks my mind from remembering.