USPS update

I've been researching the USPS after a post to my article made me question how it actually is funded. I knew that most of the funding came from the postage that we buy (and mailers, and other products they sell) but what about our tax dollars? I always assumed that we paid for the USPS from our taxes.
So, after a Google search (phrased many different ways) I am still unsure of how the USPS is funded. I found an article that reference an amount of tax money received each year by the USPS, but have no idea how they determined that.
What I did find was this:
On the USPS website, there are several speeches that have been made to Congress by the Post Master General. Many of them indicate that the Post Office is to be run as a profit neutral company, funding its daily operations from the money received from sale of stamps and products. There is nothing I can find that shows what "daily operations" encompass.
There is also a bill before Congress, requesting an amendment so they can drop a day of delivery (cutting costs) and allow them to use money (slated for 2017) from 2009-2011 to cover the cost of Retiree Health benefits. You can find this article here:
http://www.cbo.gov/ftpdocs/104xx/doc10465/hr22.pdf

If you find anything that will direct me to where I can learn about how the USPS is funded, I'd appreciate it. Always good to correct assumptions.