Quarterly report pursuant to Section 13 or 15(d)

Debt and Debt-Related Parties - Convertible Senior Unsecured Notes (Details)

v2.4.0.6
Debt and Debt-Related Parties - Convertible Senior Unsecured Notes (Details) (Convertible Senior Unsecured Notes [Member], USD $)
 3 Months Ended 6 Months Ended 6 Months Ended
Jun. 30, 2009
Jun. 30, 2012
Mar. 31, 2012
Sep. 30, 2011
Aug. 01, 2011
Jan. 01, 2009
Jul. 31, 2005
Jun. 30, 2012
Maximum [Member]
Jun. 30, 2012
Minimum [Member]
Jun. 30, 2012
Current Debt Discount [Member]
Dec. 31, 2011
Current Debt Discount [Member]
Debt Instrument [Line Items]                      
Principal amount of debt $ 204,600,000           $ 325,000,000        
Debt instrument interest rate, stated percentage             2.25%        
Debt instrument initial conversion rate, (in shares) per $1,000 principal amount             28.2326        
Debt instrument conversion price (US$ per share)             $ 35.42        
Percentage of debt principal that could be redeemed (percent)   100.00%                  
Trading period of the volume-weighted average price of stock (days)   10 days             5 days    
Volume-weighted average price of common stock (US$ per share)               $ 53.13      
Basis spread on debt instrument variable rate (percent)   0.50%                  
Aggregate debt principal amount exchanged 120,400,000                    
Value of cash and cash equivalents debt was exchanged for 30,000,000                    
Number of shares of common stock exchanged for debt 4,000,000                    
Number of shares of common stock that the remaining debt principal is convertible into     5,800,000                
Debt reclassified to currrent liability       190,700,000              
Due date of Convertible Senior Unsecured Notes         12 months            
Fair value of the embedded conversion option           134,000,000          
Unamortized debt discount                   $ 1,454,000 $ 9,906,000