Cash, Cash Equivalents, and Investments - Amortized Cost to Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 489,447
Gross Unrealized Gains	578
Gross Unrealized Losses	(680)
Fair Value, Total	489,345
Euro liquidity fund [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Total	48,235
Euro liquidity fund [Member] \| Short-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	48,229
Gross Unrealized Gains	6
Fair Value, Total	48,235
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Total	247,183
Corporate Bonds [Member] \| Short-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	30,842
Gross Unrealized Gains	50
Gross Unrealized Losses	(3)
Fair Value, Total	30,889
Corporate Bonds [Member] \| Long-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	216,404
Gross Unrealized Gains	442
Gross Unrealized Losses	(552)
Fair Value, Total	216,294
Agency Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Total	16,449
Agency Bonds [Member] \| Short-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,883
Fair Value, Total	6,883
Agency Bonds [Member] \| Long-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	9,570
Gross Unrealized Gains	4
Gross Unrealized Losses	(8)
Fair Value, Total	9,566
Supranational bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Total	1,901
Supranational bonds [Member] \| Short-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,900
Gross Unrealized Gains	1
Fair Value, Total	1,901
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Total	63,867
Asset-Backed Securities [Member] \| Short-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,311
Fair Value, Total	1,311
Asset-Backed Securities [Member] \| Long-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	62,590
Gross Unrealized Gains	18
Gross Unrealized Losses	(52)
Fair Value, Total	62,556
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Total	7,837
Municipal Bonds [Member] \| Short-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,232
Gross Unrealized Gains	5
Fair Value, Total	1,237
Municipal Bonds [Member] \| Long-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,567
Gross Unrealized Gains	33
Fair Value, Total	6,600
Treasury Bills [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Total	90,412
Treasury Bills [Member] \| Long-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	90,458
Gross Unrealized Gains	8
Gross Unrealized Losses	(54)
Fair Value, Total	90,412
Sovereign Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Total	13,461
Sovereign Bonds [Member] \| Long-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,461
Gross Unrealized Gains	11
Gross Unrealized Losses	(11)
Fair Value, Total	$ 13,461

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

No definition available.

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- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

No definition available.

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- Definition

This item represents the cost of debt 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

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-SubTopic 10

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- Definition

Amount of debt securities categorized neither as held-to-maturity nor trading.

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