Compensation and Benefit Plans (Stock-Based Compensation, Assumptions) (Details)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Stock Options
Assumptions used in pricing model
Expected term (years)	6 years 10 months 24 days		7 years
Risk-free interest rate, minimum	1.10%		1.40%
Risk-free interest rate, maximum	1.70%		3.10%
Expected dividend yield, minimum	2.80%		3.10%
Expected dividend yield, maximum	3.10%		3.50%
Weighted-average expected dividend yield	3.00%		3.40%
Expected volatility, minimum	17.00%		18.00%
Expected volatility, maximum	18.00%		19.00%
Weighted-average volatility	18.30%		18.90%
Historical period used in calculating the expected volatility (in months)	83 months		84 months
Performance Shares
Assumptions used in pricing model
Historical period used in calculating the expected volatility (in months)	36 months
Performance shares classified as equity awards
Assumptions used in pricing model
Risk-free interest rate	0.40%		1.20%
Weighted-average volatility	13.20%		20.40%
Performance shares classified as liability awards
Assumptions used in pricing model
Weighted-average volatility	12.10%	[1]	15.90%	[1]
Performance shares classified as liability awards | 2012 awards
Assumptions used in pricing model
Risk-free interest rate	0.40%	[1]
Performance shares classified as liability awards | 2011 awards
Assumptions used in pricing model
Risk-free interest rate	0.20%	[1]	0.30%	[1]

[1] The portion of performance shares classified as share-based liability awards are revalued at each reporting period.