AM can have troubles in some buildings/workplaces, as can FM.
But overall...yes (and AM, great distances at night). But 20 per cent of listening now is to AM...
another link to article in case there are problems with first one
http://ericrhoads.blogs.com/ink_tank/2013/03/a-cold-harsh-reality-for-radio.html
That's contingent on the transmitting power of the station. Growing up in northern Michigan, at night I used to listen to WLS out of Chicago as well as WJR in Detroit for it's Tiger games. Any stations in between would be non existant or static filled.
There's a station here in the Detroit area that fades out after the sun goes down and you can't listen to it........