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, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Short-term investments, Estimated Fair Value	$ 140,042	$ 299,715
Long-term investments, Estimated Fair Value	134,749	60,405
Bankers' Acceptance Drafts [Member]
Schedule of Available-for-sale Securities [Line Items]
Short-term investments, Estimated Fair Value	765	491
Time Deposits and Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Short-term investments, Estimated Fair Value	40,672	64,989
Long-term investments, Estimated Fair Value	50	54
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Short-term investments, Estimated Fair Value	9,691	53,434
Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Short-term investments, Estimated Fair Value	14,890	18,351
Long-term investments, Estimated Fair Value	61,446
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Short-term investments, Estimated Fair Value	2,099
Long-term investments, Estimated Fair Value	1,257
U.S. Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Short-term investments, Estimated Fair Value	71,925	162,450
Long-term investments, Estimated Fair Value	8,010	60,351
Asset Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Long-term investments, Estimated Fair Value	63,986
Short Term [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	139,997	299,693
Investments, Gross Unrealized Gains	50	37
Investments, Gross Unrealized (Losses)	(5)	(15)
Short-term investments, Estimated Fair Value	140,042	299,715
Short Term [Member] \| Bankers' Acceptance Drafts [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	765	491
Investments, Gross Unrealized Gains
Investments, Gross Unrealized (Losses)
Short-term investments, Estimated Fair Value	765	491
Short Term [Member] \| Time Deposits and Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	40,672	64,983
Investments, Gross Unrealized Gains	1	10
Investments, Gross Unrealized (Losses)	(1)	(4)
Short-term investments, Estimated Fair Value	40,672	64,989
Short Term [Member] \| Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	9,692	53,429
Investments, Gross Unrealized Gains	2	5
Investments, Gross Unrealized (Losses)	(3)
Short-term investments, Estimated Fair Value	9,691	53,434
Short Term [Member] \| Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	14,889	18,360
Investments, Gross Unrealized Gains	1
Investments, Gross Unrealized (Losses)		(9)
Short-term investments, Estimated Fair Value	14,890	18,351
Short Term [Member] \| Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	2,100
Investments, Gross Unrealized Gains
Investments, Gross Unrealized (Losses)	(1)
Short-term investments, Estimated Fair Value	2,099
Short Term [Member] \| U.S. Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	71,879	162,430
Investments, Gross Unrealized Gains	46	22
Investments, Gross Unrealized (Losses)		(2)
Short-term investments, Estimated Fair Value	71,925	162,450
Long Term [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	134,856	60,428
Investments, Gross Unrealized Gains	25	9
Investments, Gross Unrealized (Losses)	(132)	(32)
Long-term investments, Estimated Fair Value	134,749	60,405
Long Term [Member] \| Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	61,496
Investments, Gross Unrealized Gains	13
Investments, Gross Unrealized (Losses)	(63)
Long-term investments, Estimated Fair Value	61,446
Long Term [Member] \| Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	1,260
Investments, Gross Unrealized Gains
Investments, Gross Unrealized (Losses)	(3)
Long-term investments, Estimated Fair Value	1,257
Long Term [Member] \| U.S. Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	8,011	60,374
Investments, Gross Unrealized Gains		9
Investments, Gross Unrealized (Losses)	(1)	(32)
Long-term investments, Estimated Fair Value	8,010	60,351
Long Term [Member] \| Asset Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	64,039
Investments, Gross Unrealized Gains	12
Investments, Gross Unrealized (Losses)	(65)
Long-term investments, Estimated Fair Value	63,986
Long Term [Member] \| Time Deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	50	54
Investments, Gross Unrealized Gains
Investments, Gross Unrealized (Losses)
Long-term investments, Estimated Fair Value	$ 50	$ 54

- 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.

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