Equity (Details Textual) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Feb. 28, 2011
Class of Stock
Preferred stock, shares authorized	8,000,000	8,000,000
Equity (Textual)
Common stock shares authorized for repurchase	6,200,000			20,000,000
Repurchase of common stock, shares	7,800,000	6,000,000
Repurchase of common stock, value	$ 984,715	$ 497,975	$ 2,077,579