Hello and thank you for using just answer. I will work with you to resolve the problem you are having with your Lexus.
Typically on these cars, stalling at idle is usually only one of two things. Try cleaning the throttle body with a spray type throttle body cleaner. Carbon gets built up around the throttle plate causing a stall at idle. Usually simply cleaning the carbon will resolve the problem.
If this doesn't work, you could have a problem in the ISC valve. (idle speed control) This valve is located on the throttle body and electronically controls the idle. Try tapping on it while the car is idling and see if the idle changes at all, sometimes they stick.