Organization and Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended
Mar. 31, 2012 segment	Mar. 31, 2011	Dec. 31, 2011
Organization and Summary of Significant Accounting Policies (Textual) [Abstract]
Cash and cash equivalents, and Investment in marketable securities	$ 498,800,000
Indebtedness	240,000,000
Outstanding convertible subordinated notes	214,955,000		214,955,000
Allowance for doubtful accounts	$ 0		$ 0
Effective income tax rate	33.00%	33.00%
Number of business segments	1

Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the customer may deposit additional funds at any time and effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid Investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Short-term investments, exclusive of cash equivalents, generally consist of marketable securities intended to be sold within one year (or the normal operating cycle if longer) and may include trading securities, available-for-sale securities, or held-to-maturity securities (if maturing within one year), as applicable.

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A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

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