Share-Based Compensation (Stock Options Activity) (Detail) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Shares
Beginning balance (in shares)	2,378,559
Granted (in shares)	514,780
Exercised (in shares)	(377,056)
Forfeited/Expired (in shares)	(158,235)
Ending balance (in shares)	2,358,048	2,378,559
Vested and expected to vest (in shares)	2,242,169
Exercisable (in shares)	1,285,586
Weighted Average Price
Beginning Balance, Weighted Average Price (in dollars per share)	$ 46.91
Granted, Weighted Average Price (in dollars per share)	78.27
Exercised, Weighted Average Price (in dollars per share)	39.98
Forfeited/Expired, Weighted Average Price (in dollars per share)	65.74
Ending Balance, Weighted Average Price (in dollars per share)	53.60	$ 46.91
Vested and expected to vest , Weighted Average Price (in dollars per share)	52.62
Exercisable at September 30, 2014, Weighted Average Price (in dollars per share)	$ 41.73
Weighted-Average Remaining Contractual Term
Weighted-Average Remaining Contractual Term, Ending	6 years 9 months	6 years 8 months 9 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	6 years 7 months 21 days
Weighted-Average Remaining Contractual Term, Exercisable	5 years 3 months 29 days
Aggregate Intrinsic Value
Stock options outstanding, Beginning aggregate intrinsic value	$ 73,561,785
Stock options outstanding, Ending aggregate intrinsic value	45,576,807	$ 73,561,785
Stock options, vested and expected to vest aggregate intrinsic value	45,214,008
Stock options, exercisable aggregate intrinsic value	$ 38,206,259