Shareholders' Equity (Details Textual) (USD $)	1 Months Ended	12 Months Ended
	Jan. 31, 2008	Dec. 31, 2012	Dec. 31, 2011
Shareholders' Equity (Textual)
Common stock authorized under repurchase program	$ 200,000,000
Stock repurchase program, remaining authorized repurchase amount		68,400,000
Stock repurchased, value		0	0
Stock repurchases, shares		0	0
Common stock, shares authorized		120,000,000	120,000,000
Common stock, par value		$ 0.625	$ 0.625
Common stock, shares issued		66,021,444	65,775,568
Common stock, shares outstanding		46,898,924	46,653,048
Preferred stock, aggregate liquidation preference		900,000	1,000,000
Number of votes for each share held of common stock		1
Series A and B $2.50 Cumulative Convertible Preferred Stock [Member]
Shareholders' Equity (Textual)
Preferred stock, shares authorized		5,000,000	5,000,000
Preferred stock, par value		$ 1	$ 1
Preferred stock, shares outstanding		15,567	16,644
Cumulative annual cash dividend per share on preferred stock		$ 2.50	$ 2.5
Number of common stock issued for each convertible preferred stock		5
Redemption price per share		$ 63
Liquidation preference per share		$ 60
Preferred stock, aggregate liquidation preference		$ 900,000	$ 1,000,000