Stock Based Compensation (Details Textuals) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Stock Based Compensation (Textuals) [Abstract]
Total fair value of vested stock options	$ 5,000,000		$ 4,000,000
Average cost per share, salary share		12.99	12.41
Number of highly compensated employees to be vested in future	20
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized compensation expense for vesting of stock options	7,000,000	4,000,000	5,000,000
Unvested share-based payment awards	15,000,000
Total compensation cost not yet recognized, period for recognition	fourth quarter 2014
Restricted Stock Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized compensation expense for vesting of stock options	5,000,000	5,000,000	6,000,000
Unvested share-based payment awards	6,000,000
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 2014
Salary Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized compensation expense for vesting of stock options		$ 3,000,000	$ 4,000,000
Salary shares granted		234,969	317,450