4. Investments in Available-for-Sale Securities

The following is a summary of the Company’s investments in available-for-sale securities as of September 30, 2011:

	Cost		Unrealized Gains		Unrealized Losses			Fair Value
U.S. federal agency securities	$	35,236	$	549	$	-		$	35,785
Certificates of deposit		1,333,996		13,740		(13,452	)		1,334,284
Corporate securities		834,550		810		(18,780	)		816,580
	$	2,203,782	$	15,099	$	(32,232	)	$	2,186,649

The Company’s investment portfolio had gross realized losses of $1,778 and $938 for the nine months ended September 30, 2011 and 2010, respectively. The Company’s investment portfolio had gross realized losses of $925 and $688 for the three months ended September 30, 2011 and 2010, respectively.

The cost and fair value of investments in available-for-sale securities, by contractual maturity, as of September 30, 2011, were as follows:

	Cost		Fair Value
Due within one year	$	1,185,957	$	1,185,755
Due after one year through three years		903,911		885,629
Due after three years		113,914		115,265
	$	2,203,782	$	2,186,649

Expected maturities will differ from contractual maturities because the issuers of certain debt securities have the right to call or prepay their obligations without any penalties. Accordingly, the Company has classified the entire fair value of its investments in available-for-sale securities as current assets in the accompanying balance sheets.