Investments - Summarized Financial Assets Measured at Fair Value on Recurring Basis (Detail) (Recurring [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	$ 54,188	$ 29,108
Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	22,185	16,899
Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	32,003	12,209
Commercial Paper [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	3,999	2,998
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	3,999	2,998
Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Cash Equivalents	20,928	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	20,928	15,541
FDIC Guaranteed certificates of deposit [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	4,555	6,154
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	4,555	6,154
Common stock [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	1,257	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	1,257	1,358
Corporate notes and bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	23,449	3,057
Corporate notes and bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	$ 23,449	$ 3,057