Stock-Based Compensation - Weighted-Average Assumptions Used in Option Pricing Model (Details) (Stock Option, USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock Option
Schedule of Share-Based Compensation Award, Options, Fair Value Assumption Inputs
Weighted average grant date fair value of options granted (in dollars per share)	$ 4.06	$ 4.30	$ 4.58
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected volatility	37.46%	36.36%	35.66%
Expected dividend yield	3.35%	3.17%	2.98%
Risk-free interest rate	1.99%	3.05%	3.08%
Expected life of options (in years)	7 years 10 months 6 days	7 years 11 months 19 days	7 years 8 months 12 days