Stock Option Activity under Stock Option Plans (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Number of Shares
Beginning balance	1,035,871
Granted	46,801
Exercised	(8,750)
Cancelled	(165,536)
Ending balance	908,386
Vested and Expected to Vest at September 30, 2012	908,386
Exercisable at September 30, 2012	830,336
Weighted-Average Exercise Price
Beginning balance	$ 22.57
Granted	$ 11.69
Exercised	$ 7.69
Cancelled	$ 25.87
Ending balance	$ 21.55
Vested and Expected to Vest at September 30, 2012	$ 21.55
Exercisable at September 30, 2012	$ 22.58
Weighted Average Remaining Contractual Term
Outstanding September 30, 2012	4 years 3 months 29 days
Vested and Expected to Vest at September 30, 2012	4 years 3 months 29 days
Exercisable at September 30, 2012	3 years 10 months 21 days
Aggregate Intrinsic Value
Outstanding September 30, 2012	$ 1,097,884
Vested and Expected to Vest at September 30, 2012	1,097,884
Exercisable at September 30, 2012	$ 760,073