Equity-Based Compensation Expense - Stock-Based Compensation Plans (Detail) (USD $)	6 Months Ended
	Jun. 30, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding at beginning of period (Options)	667,036
Granted (Options)	670,450
Exercised (Options)	(92,303)
Forfeited (Options)	(16,387)
Outstanding at end of period (Options)	1,228,796
Exercisable at end of period (Options)	183,983
Outstanding at beginning of period (Weighted Avg. Exercise Price)	$ 740.18
Granted (Weighted Avg. Exercise Price)	$ 1,094.24
Exercised (Weighted Avg. Exercise Price)	$ 656.45
Forfeited (Weighted Avg. Exercise Price)	$ 830.02
Outstanding at end of period (Weighted Avg. Exercise Price)	$ 938.45
Exercisable at end of period (Weighted Avg. Exercise Price)	$ 629.72