Cash, Cash Equivalents, and Investments - Summary of Available-for-Sale Investments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 375,053
Gross Unrealized Gains	611
Gross Unrealized Losses	(1,391)
Fair Value	374,273
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	190,166
Corporate Bonds [Member] | Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	80,547
Gross Unrealized Gains	119
Gross Unrealized Losses	(280)
Fair Value	80,386
Corporate Bonds [Member] | Long-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	109,785
Gross Unrealized Gains	373
Gross Unrealized Losses	(378)
Fair Value	109,780
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	68,176
Asset-Backed Securities [Member] | Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	27,076
Gross Unrealized Gains	6
Gross Unrealized Losses	(172)
Fair Value	26,910
Asset-Backed Securities [Member] | Long-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	41,539
Gross Unrealized Gains	6
Gross Unrealized Losses	(279)
Fair Value	41,266
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	28,583
Municipal Bonds [Member] | Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,416
Gross Unrealized Gains	28
Gross Unrealized Losses	(1)
Fair Value	14,443
Municipal Bonds [Member] | Long-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,110
Gross Unrealized Gains	62
Gross Unrealized Losses	(32)
Fair Value	14,140
Sovereign Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	30,435
Sovereign Bonds [Member] | Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,396
Gross Unrealized Losses	(13)
Fair Value	7,383
Sovereign Bonds [Member] | Long-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	23,199
Gross Unrealized Gains	17
Gross Unrealized Losses	(164)
Fair Value	23,052
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	3,000
Commercial Paper [Member] | Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,000
Fair Value	3,000
Agency Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,498
Agency Bonds [Member] | Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,498
Fair Value	1,498
Treasury Bills [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	52,415
Treasury Bills [Member] | Long-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	52,487
Gross Unrealized Losses	(72)
Fair Value	$ 52,415