Stock Incentive Plans - Exercise Prices of Outstanding Options (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise prices of outstanding options, Number of options outstanding	1,926,070	2,117,110	2,093,108	1,830,397
Exercise prices of outstanding options, Average remaining contractual life	6 years 4 months 10 days
Exercise prices of outstanding options, Number of options exercisable	1,599,505
Range 1 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise prices of outstanding options, Lower range	$ 0.78
Exercise prices of outstanding options, Upper range	$ 4.94
Exercise prices of outstanding options, Number of options outstanding	533,365
Exercise prices of outstanding options, Average remaining contractual life	4 years 18 days
Exercise prices of outstanding options, Number of options exercisable	533,365
Range 2 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise prices of outstanding options, Lower range	$ 6.11
Exercise prices of outstanding options, Upper range	$ 9.58
Exercise prices of outstanding options, Number of options outstanding	385,054
Exercise prices of outstanding options, Average remaining contractual life	6 years 10 months 2 days
Exercise prices of outstanding options, Number of options exercisable	274,089
Range 3 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise prices of outstanding options, Lower range	$ 10.02
Exercise prices of outstanding options, Upper range	$ 14.00
Exercise prices of outstanding options, Number of options outstanding	374,867
Exercise prices of outstanding options, Average remaining contractual life	7 years 11 months 5 days
Exercise prices of outstanding options, Number of options exercisable	250,417
Range 4 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise prices of outstanding options, Lower range	$ 15.00
Exercise prices of outstanding options, Upper range	$ 18.80
Exercise prices of outstanding options, Number of options outstanding	66,979
Exercise prices of outstanding options, Average remaining contractual life	5 years 8 months 16 days
Exercise prices of outstanding options, Number of options exercisable	61,854
Range 5 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise prices of outstanding options, Lower range	$ 19.21
Exercise prices of outstanding options, Upper range	$ 22.92
Exercise prices of outstanding options, Number of options outstanding	375,150
Exercise prices of outstanding options, Average remaining contractual life	6 years 9 months 4 days
Exercise prices of outstanding options, Number of options exercisable	353,625
Range 6 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise prices of outstanding options, Lower range	$ 24.95
Exercise prices of outstanding options, Upper range	$ 32.67
Exercise prices of outstanding options, Number of options outstanding	190,655
Exercise prices of outstanding options, Average remaining contractual life	6 years 8 months 12 days
Exercise prices of outstanding options, Number of options exercisable	126,155