Share-Based Compensation (Stock Options Activity) (Detail) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Shares
Beginning balance (in shares)	2,378,559
Granted (in shares)	440,945
Exercised (in shares)	(238,352)
Forfeited/Expired (in shares)	(12,082)
Ending balance (in shares)	2,569,070	2,378,559
Vested and expected to vest (in shares)	2,409,629
Exercisable (in shares)	1,394,118
Weighted Average Price
Beginning Balance, Weighted Average Price (in dollars per share)	$ 46.91
Granted, Weighted Average Price (in dollars per share)	$ 78.43
Exercised, Weighted Average Price (in dollars per share)	$ 38.75
Forfeited/Expired, Weighted Average Price (in dollars per share)	$ 57.62
Ending Balance, Weighted Average Price (in dollars per share)	$ 53.03	$ 46.91
Vested and expected to vest , Weighted Average Price (in dollars per share)	$ 51.87
Exercisable at June 30, 2014, Weighted Average Price (in dollars per share)	$ 41.37
Weighted-Average Remaining Contractual Term
Weighted-Average Remaining Contractual Term, Ending	7 years 1 month 24 days	6 years 8 months 9 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	7 years 0 months 7 days
Weighted-Average Remaining Contractual Term, Exercisable	5 years 8 months 19 days
Aggregate Intrinsic Value
Stock options outstanding, Beginning aggregate intrinsic value	$ 73,561,785
Stock options outstanding, Ending aggregate intrinsic value	59,729,867	73,561,785
Stock options, vested and expected to vest aggregate intrinsic value	58,689,128
Stock options, exercisable aggregate intrinsic value	$ 48,047,309