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Investments - Gross Unrealized Gains and (Losses) Aggregated by Investment Category Short-Term and Long-Term Securities (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Short-term investments, Estimated Fair Value	$ 364,917	$ 326,862
Long-term investments, Estimated Fair Value	5,183	12,158
Short Term [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	364,844	326,601
Investments, Gross Unrealized Gains	78	267
Investments, Gross Unrealized (Losses)	(5)	(6)
Long Term [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	5,178
Investments, Gross Unrealized Gains	5
Investments, Gross Unrealized (Losses)
Bankers' Acceptance Drafts [Member]
Schedule of Available-for-sale Securities [Line Items]
Short-term investments, Estimated Fair Value	330	242
Bankers' Acceptance Drafts [Member] | Short Term [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	330	242
Investments, Gross Unrealized Gains
Investments, Gross Unrealized (Losses)
Time Deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Short-term investments, Estimated Fair Value	77,577	52
Long-term investments, Estimated Fair Value	56
Time Deposits [Member] | Short Term [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	77,575	52
Investments, Gross Unrealized Gains	5
Investments, Gross Unrealized (Losses)	(3)
Time Deposits [Member] | Long Term [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	56
Investments, Gross Unrealized Gains
Investments, Gross Unrealized (Losses)
Commercial Paper and Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Short-term investments, Estimated Fair Value	81,308
Commercial Paper and Corporate Obligations [Member] | Short Term [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	81,300
Investments, Gross Unrealized Gains	10
Investments, Gross Unrealized (Losses)	(2)
U.S. Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Short-term investments, Estimated Fair Value	205,702	313,514
Long-term investments, Estimated Fair Value	5,127	12,158
U.S. Agency Obligations [Member] | Short Term [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	205,639	313,262
Investments, Gross Unrealized Gains	63	258
Investments, Gross Unrealized (Losses)		(6)
U.S. Agency Obligations [Member] | Long Term [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	5,122	12,156
Investments, Gross Unrealized Gains	5	2
Investments, Gross Unrealized (Losses)
U.S. Treasury Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Short-term investments, Estimated Fair Value		13,054
U.S. Treasury Obligations [Member] | Short Term [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost		13,045
Investments, Gross Unrealized Gains		9
Investments, Gross Unrealized (Losses)

X

- Definition

Amount of accumulated pre-tax unrealized gains before deducting pre-tax unrealized losses on investments in available-for-sale securities impacting investments.

+ References

No definition available.

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X

- Definition

Amount of accumulated pre-tax unrealized loss before deducting pre-tax unrealized gain on investments in available-for-sale securities impacting investments.

+ References

No definition available.

+ Details

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X

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.2)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Amount of investment in debt and equity securities categorized neither as trading securities nor held-to-maturity securities and intended be sold or mature one year or operating cycle, if longer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26626-111562

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- Definition

Investments in debt and equity securities which are categorized neither as held-to-maturity nor trading and which are intended to be sold or mature more than one year from the balance sheet date or operating cycle, if longer. Such securities are reported at fair value; unrealized gains (losses) related to Available-for-sale Securities are excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain (loss) of an Available-for-sale security that is designated as being hedged in a fair value hedge is recognized in earnings during the period of the hedge, as are other than temporary declines in fair value below the cost basis for investments in equity securities and debt securities that an entity intends to sell or it is more likely than not that it will be required to sell before the recovery of its amortized cost basis. Other than temporary declines in fair value below the cost basis for debt securities categorized as Available-for-sale that an entity does not intend to sell and for which it is not more likely than not that the entity will be required to sell before the recovery of its amortized cost basis are bifurcated into credit losses and losses related to all other factors. Other than temporary declines in fair value below cost basis related to credit losses are recognized in earnings, and losses related to all other factors are recognized in other comprehensive income.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26626-111562



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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Available-for-Sale Securities

-URI http://asc.fasb.org/extlink&oid=6505594

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