Stock Based Compensation (Details Textuals) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested share-based payment awards	$ 10,000,000
Stock Based Compensation (Textuals) [Abstract]
Total fair value of vested stock options	7,000,000		9,000,000
Instrinsic value of stock options exercised	1,000,000		2,000,000
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized compensation expense for accelerated vesting of stock options	250,000
Recognized compensation expense for vesting of stock options	2,000,000	2,000,000	8,000,000
Total compensation cost not yet recognized, period for recognition	fourth quarter 2018
Restricted Stock Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized compensation expense for accelerated vesting of stock options	950,000
Recognized compensation expense for vesting of stock options	3,000,000	2,000,000	7,000,000
Unvested share-based payment awards	$ 29,000,000
Total compensation cost not yet recognized, period for recognition	fourth quarter 2018