Financial Instruments - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Financial Instruments and Fair Value [Line Items]
Realized losses on marketable securities	$ 1,400,000	$ 2,700,000	$ 3,200,000
Fair market value of investments with unrealized losses	59,100,000	64,571,000
Fair market value of investments with unrealized losses greater than one year		2,400,000
Fair market value of investments with unrealized losses less than one year		62,200,000
Unrealized Gain (loss) on contracts	100,000	(300,000)
Realized gains (losses) on foreign currency contracts	$ 4,000,000	$ (1,300,000)	$ (2,300,000)