Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements and Marketable Securities - Marketable Securities with Unrealized Losses (Detail)

v2.4.1.9
Fair Value Measurements and Marketable Securities - Marketable Securities with Unrealized Losses (Detail) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Schedule Of Available For Sale Securities [Line Items]  
Marketable securities, in loss position for less than twelve months, Fair Value $ 34,181us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
Marketable securities, in loss position for less than twelve months, Unrealized Loss (21)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
U.S. Government Securities  
Schedule Of Available For Sale Securities [Line Items]  
Marketable securities, in loss position for less than twelve months, Fair Value 12,170us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_USGovernmentDebtSecuritiesMember
Marketable securities, in loss position for less than twelve months, Unrealized Loss (2)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_USGovernmentDebtSecuritiesMember
Corporate Debt Securities  
Schedule Of Available For Sale Securities [Line Items]  
Marketable securities, in loss position for less than twelve months, Fair Value 22,011us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_CorporateDebtSecuritiesMember
Marketable securities, in loss position for less than twelve months, Unrealized Loss $ (19)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_CorporateDebtSecuritiesMember