jQuery: trigger keypress function on entire document but not inside inputs and textareas?

I have this …

$(document).keypress(function(e) {
        if ( e.keyCode === 119 ) // w
            doSomething();
    });

Wo when pressing "w" on my document the doSomething() function fires. How can I prevent it from firing when I'm currently typing (in focus) in an input field or textarea?