Investments - Summarized Financial Assets Measured at Fair Value on Recurring Basis (Detail) (Recurring [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sales securities-current	$ 34,220	$ 36,005
Money market funds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Cash Equivalents	16,280	11,644
US Treasury securities and agency [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sales securities-current	1,503	3,509
FDIC Guaranteed certificates of deposit [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sales securities-current	8,325	6,447
Common stock [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sales securities-current	2,000	2,806
Corporate Notes and Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sales securities-current	5,114	4,602
Commercial Paper [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sales securities-current	998	6,997
Fair Value, Inputs, Level 1 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sales securities-current	18,280	14,450
Fair Value, Inputs, Level 1 [Member] | Money market funds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Cash Equivalents	16,280	11,644
Fair Value, Inputs, Level 1 [Member] | Common stock [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sales securities-current	2,000	2,806
Fair Value, Inputs, Level 2 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sales securities-current	15,940	21,555
Fair Value, Inputs, Level 2 [Member] | US Treasury securities and agency [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sales securities-current	1,503	3,509
Fair Value, Inputs, Level 2 [Member] | FDIC Guaranteed certificates of deposit [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sales securities-current	8,325	6,447
Fair Value, Inputs, Level 2 [Member] | Corporate Notes and Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sales securities-current	5,114	4,602
Fair Value, Inputs, Level 2 [Member] | Commercial Paper [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sales securities-current	998	6,997
Fair Value, Inputs, Level 3 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sales securities-current
Fair Value, Inputs, Level 3 [Member] | Money market funds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Cash Equivalents
Fair Value, Inputs, Level 3 [Member] | US Treasury securities and agency [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sales securities-current
Fair Value, Inputs, Level 3 [Member] | FDIC Guaranteed certificates of deposit [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sales securities-current
Fair Value, Inputs, Level 3 [Member] | Common stock [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sales securities-current
Fair Value, Inputs, Level 3 [Member] | Corporate Notes and Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sales securities-current
Fair Value, Inputs, Level 3 [Member] | Commercial Paper [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sales securities-current