Stock Option Activity and Weighted Average Exercise Price (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Outstanding Shares
Forfeited	(2,800)
Stock Option Plans
Outstanding Shares
Beginning Balance	4,466,080	4,330,410	4,682,737
Granted	705,564	1,037,729	570,700
Exercised	(866,917)	(821,679)	(861,397)
Forfeited	(98,215)	(80,380)	(61,630)
Ending Balance	4,206,512	4,466,080	4,330,410
Vested or expected to vest at end of period	4,206,512
Options exercisable at end of period	1,640,169
Weighted-Average Exercise Price
Beginning Balance	$ 49.29	$ 35.50	$ 29.45
Granted	$ 130.10	$ 87.06	$ 66.19
Exercised	$ 30.33	$ 24.45	$ 22.54
Forfeited	$ 65.14	$ 47.55	$ 40.95
Ending Balance	$ 66.38	$ 49.29	$ 35.50
Vested or expected to vest at end of period	$ 66.38
Options exercisable at end of period	$ 32.52
Omnibus Incentive Plan
Outstanding Shares
Beginning Balance	162,431	353,572	1,098,546
Exercised	(96,398)	(191,141)	(744,974)
Ending Balance	63,233	162,431	353,572
Vested or expected to vest at end of period	63,233
Options exercisable at end of period	63,233
Weighted-Average Exercise Price
Beginning Balance	$ 23.74	$ 23.47	$ 25.08
Exercised	$ 23.77	$ 23.23	$ 25.84
Forfeited	$ 22.43
Ending Balance	$ 23.76	$ 23.74	$ 23.47
Vested or expected to vest at end of period	$ 23.76
Options exercisable at end of period	$ 23.76
Non Employee Directors, Plan
Outstanding Shares
Beginning Balance	0	16,000	80,000
Exercised	0	(16,000)	(64,000)
Forfeited			0
Ending Balance		0	16,000
Weighted-Average Exercise Price
Beginning Balance	$ 0.00	$ 27.10	$ 23.52
Exercised	$ 0.00	$ 27.10	$ 22.62
Forfeited			$ 0.00
Ending Balance		$ 0.00	$ 27.10