Schedule of Weighted Average Option, Performance Share Fair Values and Assumptions (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Stock Option
Schedule of Weighted Average Assumptions for Fair Values of Stock Options[Line Items]
Weighted average fair value of option grants (in dollars per share)	$ 15.09	$ 9.55	$ 12.94	$ 11.40
Dividend yield	1.57%	2.07%	1.57%	1.59%
Volatility	30.65%	31.96%	30.93%	32.01%
Expected life (in years)	5 years 10 months 6 days	5 years 10 months 21 days	5 years 10 months 10 days	5 years 11 months 19 days
Performance Shares
Schedule of Weighted Average Assumptions for Fair Values of Stock Options[Line Items]
Weighted average fair value of option grants (in dollars per share)			$ 50.45
Dividend yield			0.00%
Volatility			28.99%
Risk-free forward interest rate			0.40%
Expected life (in years)			2 years 10 months 13 days
Minimum | Stock Option
Schedule of Weighted Average Assumptions for Fair Values of Stock Options[Line Items]
Risk-free forward interest rate	0.11%	0.18%	0.17%	0.17%
Maximum | Stock Option
Schedule of Weighted Average Assumptions for Fair Values of Stock Options[Line Items]
Risk-free forward interest rate	4.60%	3.34%	4.12%	3.98%