Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

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- Definition

Fair value portion of borrowing which can be exchanged for a specified number of another security at the option of the issuer or the holder, for example, but not limited to, the entity's common stock.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Convertible Security

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

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- Definition

Fair value of investments in debt securities classified as held-to-maturity.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (aa)

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-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (f)

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-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (a)

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Fair value of financial and nonfinancial obligations.

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- Definition

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.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash Equivalents

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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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Represents interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value relating to contingent consideration. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

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Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Oct. 31, 2011
Assets
Federally-sponsored and corporate debt securities	$ 857,711	$ 630,698
Discounted Cash Flow \| Maximum
Liabilities
Cost of debt and weighted average cost of capital (as a percent)	16.50%	17.20%
Discounted Cash Flow \| Minimum
Liabilities
Cost of debt and weighted average cost of capital (as a percent)	8.70%	6.60%
Convertible Notes Due 2016
Liabilities
Convertible Senior Notes, stated percentage	1.00%	1.00%	1.00%
Recurring fair value measurements \| Level 1
Assets
Money market funds	145,194	77,436
Total assets	145,194	77,436
Liabilities
Convertible notes due 2016	593,750
Total liabilities	593,750
Recurring fair value measurements \| Level 2
Assets
Federally-sponsored and corporate debt securities	857,711	630,698
Total assets	857,711	630,698
Liabilities
Convertible notes due 2016		316,250
Total liabilities		316,250
Recurring fair value measurements \| Level 3
Liabilities
Contingent consideration	6,616	6,730
Total liabilities	6,616	6,730
Recurring fair value measurements \| Balance
Assets
Money market funds	145,194	77,436
Federally-sponsored and corporate debt securities	857,711	630,698
Total assets	1,002,905	708,134
Liabilities
Convertible notes due 2016	593,750	316,250
Contingent consideration	6,616	6,730
Total liabilities	$ 600,366	$ 322,980