Short-Term Investments

12 Months Ended

Dec. 31, 2011

Short-Term Investments [Abstract]

Short-Term Investments

4. SHORT-TERM INVESTMENTS

At December 31, 2011, the amortized cost, gross unrealized gain and estimated fair value of available-for-sale securities, consisting of United States treasury bills maturing in January 2012 and May 2012, were $75.0 million, $0.0 million and $75.0 million, respectively.

At December 31, 2010, the amortized cost, gross unrealized gain and estimated fair value of available-for-sale securities, consisting of a United States treasury note maturing in April 2011 was $100.0 million, $0.0 million and $100.0 million, respectively.