Probably, he's referring to this official GAO (Government Accountability Office) audit report [1] from 2011, which exposed the Fed secretly loaned 16 trillion USD (!!!) to big banks worldwide at 0% rates (afaik, currently fully unreturned).

Here are the top four [2]:

   Citigroup      - 2.5 T$
   Morgan Stanley - 2.0 T$
   Merrill Lynch  - 1.9 T$
   BOA            - 1.3 T$

Frankly, I'm surprised this didn't receive more attention from the media.

[1]: http://www.gao.gov/new.items/d11696.pdf (Table 8, PDF page 144)

[2]: http://www.sott.net/article/250592-Audit-of-the-Federal-Rese...

The numbers in those tables are an example of scary addition. Quoting from the text describing the table:

For example, an overnight PDCF loan of $10 billion that was renewed daily at the same level for 30 business days would result in an aggregate amount borrowed of $300 billion although the institution, in effect, borrowed only $10 billion over 30 days. In contrast, a TAF loan of $10 billion extended over a 1-month period would appear as $10 billion. As a result, the total transaction amounts shown in table 8 for PDCF are not directly comparable to the total transaction amounts shown for TAF and other programs that made loans for periods longer than overnight.

Your fully unreturned is incorrect, many of the loans used to create those totals were payed back the very next day after they were made.

A more interesting analysis would show a plot of the outstanding loan balance each institution maintained over time.

It's implicit in the information. Also, the PDCF is closed:

http://en.wikipedia.org/wiki/Primary_Dealer_Credit_Facility

For posterity, this page also says about the Primary Dealer Credit Facility (which is where the trillions come from in the GAO report):

All loans extended under this facility were repaid in full, with interest, in accordance with the terms of the facility.

http://www.federalreserve.gov/newsevents/reform_pdcf.htm