Stock-Based Compensation - Summary of Changes in Stock Options Outstanding (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options outstanding beginning balance at December 31, 2012, Number of Shares	56,042
Granted, Number of Shares	6,331
Exercised, Number of Shares	(4,511)
Canceled, Number of Shares	(1,808)
Options outstanding ending balance at June 30, 2013, Number of Shares	56,054
Options exercisable at June 30, 2013, Number of Shares	38,018
Options outstanding, beginning balance at December 31, 2012, Weighted-Average Exercise Price Per Share	$ 5.75
Granted, Weighted-Average Exercise Price Per Share	$ 6.89
Exercised, Weighted-Average Exercise Price Per Share	$ 3.16
Canceled, Weighted-Average Exercise Price Per Share	$ 7.90
Options outstanding, ending balance at June 30, 2013, Weighted-Average Exercise Price Per Share	$ 6.01
Options exercisable at June 30, 2013, Weighted-Average Exercise Price Per Share	$ 5.88
Options outstanding at June 30, 2013, Weighted-Average Remaining Contractual Term	3 years 6 months 26 days
Options exercisable at June 30, 2013, Weighted-Average Remaining Contractual Term	2 years 5 months 23 days
Options outstanding at June 30, 2013, Aggregate Intrinsic Value	$ 86,943
Options exercisable at June 30, 2013, Aggregate Intrinsic Value	$ 66,893