Stock Option Activity and Weighted Average Exercise Price (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock Option Plans
Outstanding Shares
Beginning Balance	4,682,737	4,308,812	2,837,800
Granted	570,700	1,276,500	1,615,812
Exercised	(861,397)	(865,875)	(6,000)
Forfeited	(61,630)	(36,700)	(138,800)
Ending Balance	4,330,410	4,682,737	4,308,812
Vested or expected to vest at end of period	4,330,410
Options exercisable at end of period	864,558
Weighted-Average Exercise Price
Beginning Balance	$ 29.45	$ 20.54	$ 16.89
Granted	$ 66.19	$ 50.52	$ 26.81
Exercised	$ 22.54	$ 16.30	$ 24.25
Forfeited	$ 40.95	$ 26.38	$ 18.79
Ending Balance	$ 35.50	$ 29.45	$ 20.54
Vested or expected to vest at end of period	$ 35.50
Options exercisable at end of period	$ 21.69
Omnibus Incentive Plan
Outstanding Shares
Beginning Balance	1,098,546	2,473,760	6,439,246
Exercised	(744,974)	(1,373,414)	(3,951,986)
Forfeited		(1,800)	(13,500)
Ending Balance	353,572	1,098,546	2,473,760
Vested or expected to vest at end of period	353,572
Options exercisable at end of period	353,572
Weighted-Average Exercise Price
Beginning Balance	$ 25.08	$ 23.36	$ 19.15
Exercised	$ 25.84	$ 21.98	$ 16.50
Forfeited		$ 24.27	$ 21.49
Ending Balance	$ 23.47	$ 25.08	$ 23.36
Vested or expected to vest at end of period	$ 23.47
Options exercisable at end of period	$ 23.47
Non Employee Directors, Plan
Outstanding Shares
Beginning Balance	80,000	104,000	176,000
Granted	8,000
Exercised	(64,000)	(16,000)	(72,000)
Forfeited		(8,000)
Ending Balance	16,000	80,000	104,000
Vested or expected to vest at end of period	16,000
Options exercisable at end of period	16,000
Weighted-Average Exercise Price
Beginning Balance	$ 23.52	$ 21.91	$ 23.03
Exercised	$ 22.62	$ 18.14	$ 24.65
Forfeited		$ 13.35
Ending Balance	$ 27.10	$ 23.52	$ 21.91
Vested or expected to vest at end of period	$ 27.10
Options exercisable at end of period	$ 27.10