Stockholders' Equity - Summary of Fair Value Assumptions for Options Granted (Details) (USD $)	6 Months Ended
	Jun. 30, 2013
April 16, 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.70%
Expected life of option in years	5 years
Expected dividend yield	1.60%
Expected stock volatility	37.42%
Estimated fair value of stock option	$ 12.66
April 17, 2012 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.90%
Expected life of option in years	5 years
Expected dividend yield	1.40%
Expected stock volatility	39.25%
Estimated fair value of stock option	$ 13.69
April 19, 2011 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.10%
Expected life of option in years	5 years
Expected dividend yield	1.60%
Expected stock volatility	39.33%
Estimated fair value of stock option	$ 11.20
April 20, 2010 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.60%
Expected life of option in years	5 years
Expected dividend yield	1.50%
Expected stock volatility	39.10%
Estimated fair value of stock option	$ 8.14
April 21, 2009 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.90%
Expected life of option in years	5 years
Expected dividend yield	1.00%
Expected stock volatility	38.80%
Estimated fair value of stock option	$ 3.64
April 15, 2008 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.70%
Expected life of option in years	5 years
Expected dividend yield	1.00%
Expected stock volatility	30.93%
Estimated fair value of stock option	$ 7.75
April 17, 2007 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	4.60%
Expected life of option in years	4 years 10 months 6 days
Expected dividend yield	1.00%
Expected stock volatility	31.59%
Estimated fair value of stock option	$ 5.63