Should not be a problem at all...
First of all, how many times have the feds searched you when you have flown??? It is pretty damn unlikely.
I've taken wads of $100 ($10k-$40k) with me on trips in my laptop bag. I've never been stopped via xray. Occasionally when I get the special pat down treatment, a TSA official will smirk or say something like nice week as I leave Vegas.
Bottom line is you can take as much money as you want with you but if it is enough that the TSA gets suspicious and calls the authorities, you need a reasonable place it came from. There have been plenty of stories of drug dealers getting stopped for traffic violations and having 6 figures seized. They can always get it back if they can prove a legal place it came from... World is a sad place when cops can seize money without you being accused of a crime, but it is the way it is.
If you are heading to casinos and you have paid taxes on the money anyways, just wire it... Any casino will open an account for you and you can pick it up there with markers... I don't mind carrying it through the airport, but it would suck if you ever get robbed... The few times I did it, I actually felt a hell of a lot better in the airport than I did on the sidewalk getting to the airport...
I should add, if you are going to carry extensive cash, it is not a bad idea to carry a copy of the bank withdrawal and/or a W2 or pay stub with you. I've never had money seized, but I would think you'd be in a much better explaining place if the feds asked and you could say I make X/year and I withdrew this from Citibank yesterday. Here's proof..
Finally, if its $20k, just put it in your pocket... $20k is less than 2 inches thick... Metal detectors don't pick up cash... Now if you took $300k, I can't imagine them not noticing...
Sean