Classification of Stock Based Compensation Expense (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Total stock-based compensation	$ 5,191		$ 5,492		$ 11,274		$ 12,906
Tax benefit associated with stock-based compensation expense	2,035	[1]	2,125	[1]	4,419	[1]	4,995	[1]
Reduction of net income	3,156		3,367		6,855		7,911
Cost Of Services
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Total stock-based compensation	217		238		450		554
Sales And Marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Total stock-based compensation	1,736		1,682		3,464		3,791
Research And Development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Total stock-based compensation	1,387		1,614		2,884		3,767
General And Administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Total stock-based compensation	$ 1,851		$ 1,958		$ 4,476		$ 4,794

[1] The recognized tax benefit related to stock-based compensation expense was estimated to be 39.2% for the three months and six months ended June 30, 2012, and 38.7% for the three months and six months ended June 30, 2011. This approximates the blended Federal and State statutory tax rate after the benefit for state taxes.