Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) (Fair Value, Measurements, Recurring [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets:
Cash equivalents	$ 5,098
Money market instruments	5,076
Corporate stock	2,131
Corporate bonds
Asset-backed securities
Treasury bills
Agency bonds
Municipal bonds
Sovereign bonds
Covered bonds
Currency forward contracts	44
Liabilities:
Currency forward contracts	14
Significant Other Observable Inputs (Level 2) [Member]
Assets:
Cash equivalents
Money market instruments
Corporate stock
Corporate bonds	146,073
Asset-backed securities	52,376
Treasury bills	42,273
Agency bonds	36,923
Municipal bonds	34,070
Sovereign bonds	14,592
Covered bonds	11,182
Currency forward contracts
Liabilities:
Currency forward contracts