Shareholders' Equity (Narrative) (Details) (USD $)	1 Months Ended	12 Months Ended		3 Months Ended	12 Months Ended
	May 31, 2010	Dec. 31, 2010	Dec. 31, 2011	Jun. 30, 2009 Preferred Stock Series B [Member]	Dec. 31, 2011 Preferred Stock Series B [Member]
Class of Stock [Line Items]
Repurchase of common stock	4,300,000	7,884,597	7,468,869
Common stock price per share	$ 35.00
Proceeds from issuance of common stock	$ 143,300,000	$ 143,325,000
Reduction to retained earnings	42,800,000
Treasury stock historical value	186,100,000
Preferred stock annual dividend per share					$ 12.93
Stock price at which preferred stock converted into common stock				152.10
Treasury stock issued to convert into preferred stock, value				93,800,000
Treasury stock issued to convert into preferred stock, shares				2,202,937
Outstanding preferred stock, value				75,000,000
Outstanding preferred stock, shares				493,220
Difference between the historical cost of the treasury stock and the converted preferred stock				18,800,000
Treasury stock used to pay the common-stock, value				4,000,000
Treasury stock used to pay the common-stock, shares				93,636
Accrued cash dividend on preferred stock				3,200,000
Reduction to additional paid-in capital in common shareholders' equity				$ 800,000