XML 72 R57.htm IDEA: XBRL DOCUMENT v3.6.0.2
Shareholders' equity (Details) - USD ($)
 12 Months Ended 20 Months Ended 60 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2016
Dec. 31, 2015
Jun. 30, 2016
Mar. 31, 2015
Dec. 31, 2011
Dec. 31, 2008
Class of Stock [Line Items]                  
Common stock, shares authorized (shares) 195,000,000 195,000,000   195,000,000 195,000,000        
Common stock, par value (in dollars per share) $ 0.01 $ 0.01   $ 0.01 $ 0.01        
Common stock, shares issued (shares) 94,437,418 94,224,571   94,437,418 94,224,571        
Common stock, shares outstanding (shares) 87,250,897 87,038,050   87,250,897 87,038,050        
Preferred stock, shares authorized (shares) 5,000,000 5,000,000   5,000,000 5,000,000        
Preferred stock, shares issued (shares)                 160,000
Preferred stock, par value (in dollars per share) $ 0.01 $ 0.01   $ 0.01 $ 0.01        
Liquidation preference (in dollars per share) $ 0.01     $ 0.01          
Conversion of convertible preferred stock (shares) 100     100   100      
Authorized repurchase amount $ 130,000,000     $ 130,000,000       $ 60,000,000  
Additional repurchase amount             $ 70,000,000    
Treasury stock acquired, Aggregate purchase price   $ 36,352,000     $ 86,276,000        
Stock repurchase program, Remaining authorized repurchase amount $ 43,724,000     $ 43,724,000          
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Repurchase of common stock (shares)       0 7,186,521        
Series A Convertible Preferred Stock [Member]                  
Class of Stock [Line Items]                  
Preferred stock, shares outstanding (shares) 75,625 76,539   75,625 76,539        
Preferred stock, par value (in dollars per share) $ 0.01     $ 0.01          
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Beginning balance (shares) 76,539 78,141 79,620            
Repurchase of common stock (shares)   0              
Conversion of convertible preferred stock (shares) (914) (1,602) (1,479)            
Issuance for share-based compensation plans (shares) 0 0 0            
Ending balance (shares) 75,625 76,539 78,141 75,625 76,539        
Treasury [Member]                  
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Beginning balance (shares) 7,186,521 4,786,521 4,786,521            
Repurchase of common stock (shares)   2,400,000              
Conversion of convertible preferred stock (shares) 0 0 0            
Issuance for share-based compensation plans (shares) 0 0 0            
Ending balance (shares) 7,186,521 7,186,521 4,786,521 7,186,521 7,186,521        
Common stock [Member]                  
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Beginning balance (shares) 87,038,050 89,064,582 88,710,277            
Repurchase of common stock (shares)   (2,400,000)              
Conversion of convertible preferred stock (shares) 91,362 160,162 147,952            
Issuance for share-based compensation plans (shares) 121,485 213,306 206,353            
Ending balance (shares) 87,250,897 87,038,050 89,064,582 87,250,897 87,038,050