Stock Option Activity under Stock Option Plans (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2012
Number of Shares
Beginning balance	1,035,871
Granted	33,301
Cancelled	(2,768)
Ending balance	1,066,404
Vested and Expected to Vest at June 30, 2012	1,066,404
Exercisable at June 30, 2012	999,104
Weighted-Average Exercise Price
Beginning balance	$ 22.57
Granted	$ 11.38
Cancelled	$ 19.00
Ending balance	$ 22.23
Vested and Expected to Vest at June 30, 2012	$ 22.23
Exercisable at June 30, 2012	$ 23.04
Weighted Average Remaining Contractual Term
Outstanding June 30, 2012	4 years 6 months 11 days
Vested and Expected to Vest at June 30, 2012	4 years 18 days
Exercisable at June 30, 2012	4 years 2 months 5 days
Aggregate Intrinsic Value
Outstanding June 30, 2012	$ 609,772
Vested and Expected to Vest at June 30, 2012	609,772
Exercisable at June 30, 2012	$ 462,023