Shareholders' Equity (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 25, 2019
Shareholders' Equity (Textual)
Common stock authorized under repurchase program				$ 300,000,000
Stock repurchases, Shares	1,500,000	1,700,000	2,700,000
Payments for stock repurchases	$ (115,500,000)	$ (100,000,000)	$ (120,100,000)
Common stock, shares authorized	120,000,000	120,000,000
Common Stock, Par or Stated Value Per Share	$ 0.625	$ 0.625
Common stock, shares issued	67,329,081	67,083,149
Common stock, shares outstanding	36,612,227	37,895,641
Series A and B $2.50 Cumulative Convertible Preferred Stock [Member]
Shareholders' Equity (Textual)
Preferred stock, shares authorized	5,000,000
Preferred stock, par value	$ 1.00