Concentration of Credit Risk

9 Months Ended

Sep. 30, 2011

Concentration of Credit Risk [Abstract]

Concentration of Credit Risk

Concentration of Credit Risk

Financial instruments that subject the Company to credit risk consist of cash and cash equivalents, marketable securities and accounts receivable. The Company maintains the majority of its cash, cash equivalents and marketable securities balances principally with domestic financial institutions that the Company believes are of high credit standing.

At September 30, 2011 and December 31, 2010, the Company held ARS, with an estimated fair value of $118.8 million and $137.3 million, respectively, that have experienced failed auctions preventing the Company from liquidating those investments. Based on its ability to access its cash and short-term investments and its expected cash flows, the Company does not anticipate the current lack of liquidity with respect to these ARS to have a material impact on its financial condition or results of operations during 2011. As of September 30, 2011, the Company had recorded a pre-tax cumulative unrealized loss of $16.6 million related to the temporary impairment of the ARS, which was included in accumulated other comprehensive income (loss) withing stockholders' equity on its consolidated balance sheet. See Note 4.

Concentrations of credit risk with respect to accounts receivable are limited to certain customers to which the Company makes substantial sales. The Company’s customer base consists of a large number of geographically dispersed customers diversified across numerous industries. To reduce risk, the Company routinely assesses the financial strength of its customers. Based on such assessments, the Company believes that its accounts receivable credit risk exposure is limited. As of September 30, 2011 and December 31, 2010, one customer accounted for more than 10% of the Company's accounts receivable. The Company believes that, at September 30, 2011, concentration of credit risk related to accounts receivable was not significant.