Stock Compensation Plans and Other Compensation Arrangements (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	1 Months Ended	3 Months Ended
	Feb. 28, 2013	Mar. 31, 2013
Restricted Stock Rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, cash units, or cash performance units granted	400
Vesting period of stock awards		3 years
Restricted Performance Stock Rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, cash units, or cash performance units granted	1,100
Vesting period of stock awards		3 years
Restricted Stock Rights and Restricted Performance Stock Rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to unvested awards	96
Cash Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, cash units, or cash performance units granted	30,000
Vesting period of stock awards		3 years
Cash Performance Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, cash units, or cash performance units granted	69,000
Vesting period of stock awards		3 years
Minimum | Cash Units and Cash Performance Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to unvested awards	30
Maximum | Cash Units and Cash Performance Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to unvested awards	168