Investments - Summarized Financial Assets Measured at Fair Value on Recurring Basis (Detail) (Recurring [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	$ 59,511	$ 29,108
Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	25,139	16,899
Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	34,372	12,209
Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current
Commercial Paper [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	5,996	2,998
Commercial Paper [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current
Commercial Paper [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	5,996	2,998
Commercial Paper [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current
Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Cash Equivalents	24,030	15,541
Money market funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Cash Equivalents	24,030	15,541
Money market funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Cash Equivalents
Money market funds [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Cash Equivalents
FDIC Guaranteed certificates of deposit [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	4,238	6,154
FDIC Guaranteed certificates of deposit [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current
FDIC Guaranteed certificates of deposit [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	4,238	6,154
FDIC Guaranteed certificates of deposit [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current
Common stock [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	1,109	1,358
Common stock [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	1,109	1,358
Common stock [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current
Common stock [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current
Corporate notes/bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	24,138	3,057
Corporate notes/bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current
Corporate notes/bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	24,138	3,057
Corporate notes/bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current