Employee Stock Based Incentives - Long-Term Incentive Plans (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	1 Months Ended	12 Months Ended
	Jan. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Long-Term Incentive Plan
Employee stock-based awards general disclosures
Shares of common stock available for issuance		283
Stock Appreciation Rights (SARs) [Member] | Chief Executive Officer [Member]
Employee stock-based awards general disclosures
Deferred Compensation Arrangement with Individual, Shares Authorized for Issuance		2
Period Over Which Vesting is Deferred	18 months
Deferred Compensation Arrangement with Individual, Exercise Price		$ 39.83
Deferred Compensation Arrangement with Individual, Requisite Service Period		six and one-half years
Total noncash compensation expense related to employee stock-based incentive plans		$ 5	$ (4)	$ 4