Share-Based Compensation (Stock Options Activity) (Detail) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Shares
Beginning balance (in shares)	2,378,559
Granted (in shares)	459,830
Exercised (in shares)	(338,195)
Forfeited/Expired (in shares)	(53,310)
Ending balance (in shares)	2,446,884	2,378,559
Vested and expected to vest (in shares)	2,309,595
Exercisable (in shares)	1,317,492
Weighted Average Price
Beginning Balance, Weighted Average Price (in dollars per share)	$ 46.91
Granted, Weighted Average Price (in dollars per share)	78.40
Exercised, Weighted Average Price (in dollars per share)	39.93
Forfeited/Expired, Weighted Average Price (in dollars per share)	61.85
Ending Balance, Weighted Average Price (in dollars per share)	53.47	$ 46.91
Vested and expected to vest , Weighted Average Price (in dollars per share)	52.41
Exercisable at June 30, 2014, Weighted Average Price (in dollars per share)	$ 41.61
Weighted-Average Remaining Contractual Term
Weighted-Average Remaining Contractual Term, Ending	6 years 11 months 12 days	6 years 8 months 9 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	6 years 9 months 29 days
Weighted-Average Remaining Contractual Term, Exercisable	5 years 6 months 7 days
Aggregate Intrinsic Value
Stock options outstanding, Beginning aggregate intrinsic value	$ 73,561,785
Stock options outstanding, Ending aggregate intrinsic value	61,436,539	$ 73,561,785
Stock options, vested and expected to vest aggregate intrinsic value	60,453,367
Stock options, exercisable aggregate intrinsic value	$ 48,706,596