Stock-Based Compensation - Assumptions Used to Determine the Fair Value of the Awards with Market-Based (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Share Based Compensation Arrangement by Share Based Payment Award Fair Value Assumptions and Methodology [Line Items]
Expected dividends per share	$ 1.10	$ 0.90	$ 1.10	$ 0.90
Expected volatility, minimum	42.10%	41.50%	42.10%	41.50%
Expected volatility, maximum	42.60%	48.70%	42.60%	51.60%
Risk-free interest rate, minimum	0.10%	0.00%	0.10%	0.00%
Risk-free interest rate, maximum	1.50%	1.10%	1.50%	1.10%
Estimated cost of capital	11.50%	9.90%	11.50%
Estimated cost of capital, minimum				9.30%
Estimated cost of capital, maximum				9.90%
Expected life (in years)	4 years	4 years	4 years
Minimum [Member]
Share Based Compensation Arrangement by Share Based Payment Award Fair Value Assumptions and Methodology [Line Items]
Expected life (in years)				4 years
Maximum [Member]
Share Based Compensation Arrangement by Share Based Payment Award Fair Value Assumptions and Methodology [Line Items]
Expected life (in years)				6 years