Fair Value Measurements - (Narrative) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	$ 8,354	$ 5,349
Short-term investments	15,105	15,105
Investment maturity date range, start	2017
Investment maturity date range, end	2042
Variable rate demand notes puttable notice period	7 days
Financial assets, fair value disclosure	23,459	20,454
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets, fair value disclosure	0	0
Financial liabilities, fair value disclosure	0	0
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets, fair value disclosure	0	0
Financial liabilities, fair value disclosure	$ 0	$ 0