Stock Based Compensation (Details Textuals) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Stock Based Compensation (Textuals) [Abstract]
Total fair value of vested stock options	$ 8		$ 5
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized compensation expense for vesting of stock options	2	2	9
Unvested share-based payment awards	14
Total compensation cost not yet recognized, period for recognition	fourth quarter 2015
Restricted Stock Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized compensation expense for vesting of stock options	2	2	7
Unvested share-based payment awards	$ 20
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation cost not yet recognized, period for recognition	fourth quarter 2015