Share-Based Compensation (Expenses Associated with Share-Based Compensation Plans) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation	$ 4,698	$ 3,443	$ 20,261	$ 15,962
RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation	4,059	2,910	18,278	14,275
Stock options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation	68	68	203	203
Employee stock purchase plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation	$ 571	$ 465	$ 1,780	$ 1,484