Cash Equivalents and Investments (Narrative) (Detail) (USD $)	3 Months Ended	6 Months Ended
Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Cash and Cash Equivalents [Abstract]
Gains (losses) on sales of available-for-sale securities	$ 0		$ 0	$ 0	$ 0
Other-than-temporary impairments on available-for-sale securities	$ 0	$ 0

The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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Reference 7: 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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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