Quarterly report pursuant to Section 13 or 15(d)

Per Share Data and Stockholders' Equity (Details Textual)

v2.4.0.6
Per Share Data and Stockholders' Equity (Details Textual)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
5.0% Convertible Senior Notes [Member]
   
Capital Structure and Per Share Data (Textual) [Abstract]    
Stated Interest rate on debt agreement 5.00%  
Convertible senior notes maturity Year 2029  
Common Class A [Member]
   
Capital Structure and Per Share Data (Textual) [Abstract]    
Antidilutive stock options excluded in computation of diluted earnings per share 0.9 1.6