Cash, Cash Equivalents, and Investments - Gross Unrealized Losses and Fair Values for Available-for-Sale Investments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	$ 245,885
Unrealized Losses, Less than 12 Months	(1,389)
Fair Value, 12 Months or Greater	1,570
Unrealized Losses, 12 Months or Greater	(2)
Total Fair Value	247,455
Total Unrealized Losses	(1,391)
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	107,235
Unrealized Losses, Less than 12 Months	(658)
Total Fair Value	107,235
Total Unrealized Losses	(658)
Sovereign Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	23,007
Unrealized Losses, Less than 12 Months	(177)
Total Fair Value	23,007
Total Unrealized Losses	(177)
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	5,846
Unrealized Losses, Less than 12 Months	(33)
Total Fair Value	5,846
Total Unrealized Losses	(33)
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	59,180
Unrealized Losses, Less than 12 Months	(449)
Fair Value, 12 Months or Greater	1,570
Unrealized Losses, 12 Months or Greater	(2)
Total Fair Value	60,750
Total Unrealized Losses	(451)
Treasury Bills [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	50,617
Unrealized Losses, Less than 12 Months	(72)
Total Fair Value	50,617
Total Unrealized Losses	$ (72)