Investments - Summarized Financial Assets Measured at Fair Value on Recurring Basis (Detail) (Recurring [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available For Sale Securities -current	$ 31,884	$ 36,005
Money market funds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Cash Equivalents	16,988	11,644
US Treasury securities and agency [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available For Sale Securities -current		3,509
FDIC Guaranteed certificates of deposit [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available For Sale Securities -current	7,114	6,447
Common stock [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available For Sale Securities -current	1,644	2,806
Corporate Notes/Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available For Sale Securities -current	5,139	4,602
Commercial Paper [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available For Sale Securities -current	999	6,997
Fair Value, Inputs, Level 1 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available For Sale Securities -current	18,632	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	16,988	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 Sale Securities -current	1,644	2,806
Fair Value, Inputs, Level 2 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available For Sale Securities -current	13,252	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 Sale Securities -current		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 Sale Securities -current	7,114	6,447
Fair Value, Inputs, Level 2 [Member] | Corporate Notes/Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available For Sale Securities -current	5,139	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 Sale Securities -current	999	6,997
Fair Value, Inputs, Level 3 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available For Sale 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 Sale 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 Sale 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 Sale Securities -current
Fair Value, Inputs, Level 3 [Member] | Corporate Notes/Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available For Sale 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 Sale Securities -current