Fair Value of Financial Instruments and Non-Financial Assets (Tables)

12 Months Ended

Dec. 31, 2013

Schedule of Fair Value - Assets Measured on Recurring Basis

The following tables set forth by level within the fair value hierarchy the Company's assets and liabilities that were recorded at fair value as of December 31, 2013 and December 31, 2012 (in thousands). As required by the guidance for fair value measurements, financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Thus, assets and liabilities categorized as Level 3 may be measured at fair value using inputs that are observable (Levels 1 and 2) and unobservable (Level 3). Management's assessment of the significance of a particular input to the fair value measurement requires judgment, which may affect the valuation of assets and liabilities and their placement within the fair value hierarchy levels.



	At Fair Value as of December 31, 2013
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds	$	—	$	12,144	$	—	$	12,144
Commercial paper	—		191,989		—		191,989
U.S. government or government agency securities	—		306,808		—		306,808
Total	$	—	$	510,941	$	—	$	510,941



	At Fair Value as of December 31, 2012
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds	$	—	$	126,617	$	—	$	126,617
Commercial paper	—		82,346		—		82,346
U.S. government or government agency securities	—		135,861		—		135,861
Total	$	—	$	344,824	$	—	$	344,824

Schedule of Available-for-sale Securities

Available-for-sale securities were comprised as follows as of December 31, 2013 and December 31, 2012 (in thousands):



	As of December 31, 2013
	Cost		Fair Value
Money market funds	$	12,144	$	12,144
Commercial paper	191,989		191,989
U.S. government or government agency securities	306,813		306,808
	$	510,946	$	510,941



	As of December 31, 2012
	Cost		Fair Value
Money market funds	$	126,617	$	126,617
Commercial paper	82,345		82,346
U.S. government or government agency securities	135,848		135,861
	$	344,810	$	344,824

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References

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

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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Reference 9: http://www.xbrl.org/2003/role/presentationRef

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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.

Reference 10: http://www.xbrl.org/2003/role/presentationRef

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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.

+ Details