Stock Compensation Plans and Other Compensation Arrangements (Unaudited) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	9 Months Ended
	Feb. 28, 2013	Sep. 30, 2013
Restricted Stock Rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of stock awards		3 years
Cash Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of stock awards		3 years
Restricted Stock Rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, cash units, or cash performance units granted	0.4
Restricted Performance Stock Rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, cash units, or cash performance units granted	1.1
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	30.0
Cash Performance Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, cash units, or cash performance units granted	69.0
Vesting period of stock awards		3 years
Cash Units and Cash Performance Units | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to unvested awards	30
Cash Units and Cash Performance Units | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to unvested awards	$ 168