Stock Option Activity under Stock Option Plans (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Number of Shares
Beginning balance	906,636
Granted	9,000
Exercised	(2,250)
Cancelled	(8,471)
Ending balance	904,915
Vested and Expected to Vest at March 31, 2013	904,915
Exercisable at March 31, 2013	867,615
Weighted-Average Exercise Price
Beginning balance	$ 21.58
Granted	$ 15.32
Exercised	$ 6.99
Cancelled	$ 24.69
Ending balance	$ 21.60
Vested and Expected to Vest at March 31, 2013	$ 21.60
Exercisable at March 31, 2013	$ 22.00
Weighted Average Remaining Contractual Term
Outstanding March 31, 2013	3 years 10 months 13 days
Vested and Expected to Vest at March 31, 2013	3 years 10 months 13 days
Exercisable at March 31, 2013	3 years 7 months 21 days
Aggregate Intrinsic Value
Outstanding March 31, 2013	$ 1,140,887
Vested and Expected to Vest at March 31, 2013	1,140,887
Exercisable at March 31, 2013	$ 1,023,790