Investments - Gross Unrealized Gains and (Losses) Aggregated by Investment Category Short-Term and Long-Term Securities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Short-term investments, Estimated Fair Value	$ 129,594	$ 299,715
Long-term investments, Estimated Fair Value	157,201	60,405
Short Term [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	129,600	299,693
Investments, Gross Unrealized Gains	16	37
Investments, Gross Unrealized (Losses)	(22)	(15)
Short-term investments, Estimated Fair Value	129,594	299,715
Short Term [Member] \| Time Deposits and Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	20,901	64,983
Investments, Gross Unrealized Gains		10
Investments, Gross Unrealized (Losses)	(1)	(4)
Short-term investments, Estimated Fair Value	20,900	64,989
Short Term [Member] \| Bankers Acceptance Drafts [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	82	491
Short-term investments, Estimated Fair Value	82	491
Short Term [Member] \| Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	24,029	18,360
Investments, Gross Unrealized Gains	2
Investments, Gross Unrealized (Losses)	(11)	(9)
Short-term investments, Estimated Fair Value	24,020	18,351
Short Term [Member] \| Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	2,100
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	82,488	162,430
Investments, Gross Unrealized Gains	14	22
Investments, Gross Unrealized (Losses)	(9)	(2)
Short-term investments, Estimated Fair Value	82,493	162,450
Short Term [Member] \| Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost		53,429
Investments, Gross Unrealized Gains		5
Short-term investments, Estimated Fair Value		53,434
Long Term [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	157,489	60,428
Investments, Gross Unrealized Gains	8	9
Investments, Gross Unrealized (Losses)	(296)	(32)
Long-term investments, Estimated Fair Value	157,201	60,405
Long Term [Member] \| Time Deposits and Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost		54
Long-term investments, Estimated Fair Value		54
Long Term [Member] \| Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	64,842
Investments, Gross Unrealized Gains	1
Investments, Gross Unrealized (Losses)	(174)
Long-term investments, Estimated Fair Value	64,669
Long Term [Member] \| Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	1,258
Investments, Gross Unrealized (Losses)	(4)
Long-term investments, Estimated Fair Value	1,254
Long Term [Member] \| U.S. Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	15,563	60,374
Investments, Gross Unrealized Gains	2	9
Investments, Gross Unrealized (Losses)	(9)	(32)
Long-term investments, Estimated Fair Value	15,556	60,351
Long Term [Member] \| Time Deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	48
Long-term investments, Estimated Fair Value	48
Long Term [Member] \| Asset Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	75,778
Investments, Gross Unrealized Gains	5
Investments, Gross Unrealized (Losses)	(109)
Long-term investments, Estimated Fair Value	$ 75,674

- 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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