Cash Equivalents and Investments - Contractual Maturities of Available-for-Sale Debt Securities (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Investments Debt And Equity Securities [Abstract]
Due within one year	$ 29,424
Due in 1-5 years	59,264
Due in 5-10 years	10,497
Due after 10 years	134,120
Total	$ 233,305	$ 204,457

Total of debt securities categorized neither as held-to-maturity nor trading which are intended be sold or mature within one year from the balance sheet date or the normal operating cycle, whichever is longer.

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

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+ Details