Financial Assets Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value on recurring basis	$ 102,391	$ 85,557
Carrying Amount | Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value on recurring basis	102,173	85,343
Carrying Amount | Marketable Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value on recurring basis	218	214
Fair Value Measurements, Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value on recurring basis	102,391	85,557
Fair Value Measurements, Level 1 | Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value on recurring basis	102,173	85,343
Fair Value Measurements, Level 1 | Marketable Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value on recurring basis	$ 218	$ 214