Summary of Company Cash , Cash Equivalents and Short-term Investments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Cash and Cash Equivalents [Line Items]
Cash, cash equivalents and short-term investments, Amortized cost	$ 225,251	$ 256,965
Cash, cash equivalents and short-term investments, Gross unrealized gains	5
Cash, cash equivalents and short-term investments, Gross unrealized losses	(64)
Cash, cash equivalents and short-term investments, Fair market value	225,192	256,965
Cash and Cash Equivalents
Cash and Cash Equivalents [Line Items]
Cash, cash equivalents and short-term investments, Amortized cost	49,101	256,965
Cash, cash equivalents and short-term investments, Gross unrealized gains
Cash, cash equivalents and short-term investments, Gross unrealized losses
Cash, cash equivalents and short-term investments, Fair market value	49,101	256,965
Short-term Investments
Cash and Cash Equivalents [Line Items]
Cash, cash equivalents and short-term investments, Amortized cost	176,150
Cash, cash equivalents and short-term investments, Gross unrealized gains	5
Cash, cash equivalents and short-term investments, Gross unrealized losses	(64)
Cash, cash equivalents and short-term investments, Fair market value	176,091
Cash, Money Market Funds, Commercial Paper and Government and Government Agency Bonds [Member]
Cash and Cash Equivalents [Line Items]
Cash, cash equivalents and short-term investments, Amortized cost	49,101
Cash, cash equivalents and short-term investments, Gross unrealized gains
Cash, cash equivalents and short-term investments, Gross unrealized losses
Cash, cash equivalents and short-term investments, Fair market value	49,101
Commercial Paper
Cash and Cash Equivalents [Line Items]
Cash, cash equivalents and short-term investments, Amortized cost	24,892
Cash, cash equivalents and short-term investments, Gross unrealized gains	1
Cash, cash equivalents and short-term investments, Gross unrealized losses	(3)
Cash, cash equivalents and short-term investments, Fair market value	24,890
Government And Government Agency Bonds [Member]
Cash and Cash Equivalents [Line Items]
Cash, cash equivalents and short-term investments, Amortized cost	88,755
Cash, cash equivalents and short-term investments, Gross unrealized gains	4
Cash, cash equivalents and short-term investments, Gross unrealized losses	(14)
Cash, cash equivalents and short-term investments, Fair market value	88,745
Corporate Bonds
Cash and Cash Equivalents [Line Items]
Cash, cash equivalents and short-term investments, Amortized cost	62,503
Cash, cash equivalents and short-term investments, Gross unrealized gains
Cash, cash equivalents and short-term investments, Gross unrealized losses	(47)
Cash, cash equivalents and short-term investments, Fair market value	62,456
Cash and Money Market Funds [Member]
Cash and Cash Equivalents [Line Items]
Cash, cash equivalents and short-term investments, Amortized cost		256,965
Cash, cash equivalents and short-term investments, Gross unrealized gains
Cash, cash equivalents and short-term investments, Gross unrealized losses
Cash, cash equivalents and short-term investments, Fair market value		$ 256,965