I'll make that easy....from US Customs Service:
"If you are traveling to the U.S. or a foreign country carrying negotiable monetary instruments valued at $10,000 or more, you are required to declare it to CBP on your Customs declaration (CBP 6059B). In addition, you are required to file the FinCEN Form 105 with CBP upon your departure or entry into the U.S. If you filled out the FinCEN Form 105, but were unable to give it to the CBP officer at the port of departure or arrival due to circumstances out of your control, it is advised that you forward it to CBP as soon as possible with a written explanation.
Failure to report negotiable monetary instruments in amounts over $10,000 may be subject to forfeiture and could result to civil or criminal penalties."
Here's the form and instructions!
http://www.fincen.gov/forms/files/fin105_cmir.pdf