Investments - Summarized Financial Assets Measured at Fair Value on Recurring Basis (Detail) (Recurring [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	$ 29,108	$ 36,005
Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	16,899	14,450
Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	12,209	21,555
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	2,998	6,997
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	2,998	6,997
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	15,541	11,644
Money market funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Cash Equivalents	15,541	11,644
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
US Treasury securities and agency [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current		3,509
US Treasury securities and agency [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current
US Treasury securities and agency [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current		3,509
US Treasury securities and agency [Member] | Fair Value, Inputs, Level 3 [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 Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities-current	6,154	6,447
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	6,154	6,447
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	1,358	2,806
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	1,358	2,806
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	3,057	4,602
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	3,057	4,602
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