Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Discounted Cash Flow \| Maximum
Liabilities
Cost of debt and weighted average cost of capital (as a percent)	17.20%	17.90%
Discounted Cash Flow \| Minimum
Liabilities
Cost of debt and weighted average cost of capital (as a percent)	6.60%	8.60%
Recurring fair value measurements \| Level 1
Assets
Money market funds	77,436	72,905
Available-for-sale equity investment	473	382
Total assets	77,909	73,287
Recurring fair value measurements \| Level 2
Assets
Federally-sponsored and corporate debt securities	630,698	583,976
Total assets	630,698	583,976
Liabilities
Total liabilities	316,250	292,500
Recurring fair value measurements \| Level 2 \| Convertible Notes Due 2016
Liabilities
Convertible Senior Notes	316,250	292,500
Recurring fair value measurements \| Level 3
Liabilities
Contingent consideration	6,730	7,973
Total liabilities	6,730	7,973
Recurring fair value measurements \| Balance
Assets
Money market funds	77,436	72,905
Federally-sponsored and corporate debt securities	630,698	583,976
Available-for-sale equity investment	473	382
Total assets	708,607	657,263
Liabilities
Contingent consideration	6,730	7,973
Total liabilities	322,980	300,473
Recurring fair value measurements \| Balance \| Convertible Notes Due 2016
Liabilities
Convertible Senior Notes	316,250	292,500

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

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-Glossary Convertible Security

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an 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.

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-Glossary Cash Equivalents

-URI http://asc.fasb.org/extlink&oid=6507016

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-Name Statement of Financial Accounting Standard (FAS)

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Fair value, as of the balance sheet date, of potential payments under the contingent consideration arrangement including cash and shares.

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