Share-Based Compensation Option Assumptions (Details)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock options granted under the Company's option plans
Expected term	5 years 9 months 18 days	5 years 8 months 6 days	5 years 10 months 18 days
Stock volatility	36.60%	40.40%	40.90%
Risk free interest rates	1.00%	1.70%	2.20%
Dividends during expected terms	1.60%	1.40%	1.30%