Shareholders' Equity (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended
	Jan. 31, 2008	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Shareholders' Equity (Additional) (Textual)
Common stock authorized under repurchase program	$ 200
Stock repurchased, value		0	0	55.1
Stock repurchases, Shares		0	0	2,800,000
Common stock, par value		$ 0.625	$ 0.625
Common stock, shares authorized		120,000,000	120,000,000
Common stock, shares issued		65,775,568	65,482,950
Common stock, shares outstanding		46,653,048	46,360,430
Number of votes for each share held of common stock		one
Series A and B $2.50 Cumulative Convertible Preferred Stock [Member]
Shareholders' Equity (Textual)
Preferred stock, par value		$ 1.00	$ 1.00
Preferred stock, shares authorized		5,000,000	5,000,000
Preferred stock, shares outstanding		16,644	16,694
Cumulative annual cash dividend per share on preferred stock		$ 2.50
Number of common stock issued for each convertible preferred stock		5
Redemption price per share		$ 63.00
Liquidation preference per share		$ 60.00
Preferred stock, aggregate liquidation preference		$ 1.0	$ 1.0
Number of votes for each share held of preferred stock		one