- Stock Option Activity and Weighted Average Exercise Price (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Outstanding Shares
Forfeited	0
Stock Option Plans
Outstanding Shares
Beginning Balance	4,893,951	4,717,061	4,105,539
Granted	806,698	1,267,812	1,326,430
Exercised	(724,124)	(898,417)	(348,206)
Forfeited	(400,599)	(192,505)	(366,702)
Ending Balance	4,575,926	4,893,951	4,717,061
Vested or expected to vest at end of period	4,575,926
Options exercisable at end of period	1,909,271
Weighted-Average Exercise Price
Beginning Balance	$ 91.78	$ 84.32	$ 84.61
Granted	115.43	88.22	78.72
Exercised	61.49	44.18	40.51
Forfeited	105.70	108.15	108.90
Ending Balance	99.53	$ 91.78	$ 84.32
Vested or expected to vest at end of period	99.53
Options exercisable at end of period	$ 99.47
Omnibus Incentive Plan
Outstanding Shares
Beginning Balance	0	0	18,950
Exercised	0	0	(18,950)
Forfeited		0	0
Ending Balance	0	0	0
Vested or expected to vest at end of period	0
Options exercisable at end of period	0
Weighted-Average Exercise Price
Beginning Balance	$ 0.00	$ 0.00	$ 23.37
Exercised	0.00	0.00	23.37
Forfeited	0.00	0.00	0
Ending Balance	0.00	$ 0.00	$ 0.00
Vested or expected to vest at end of period	0.00
Options exercisable at end of period	$ 0.00