v2.4.0.6
Earnings per Share (Details) (USD $)
 3 Months Ended 9 Months Ended 3 Months Ended 9 Months Ended 3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Performance Share Awards Under the Equity Incentive Compensation Plan
Sep. 30, 2012
Performance Share Awards Under the Equity Incentive Compensation Plan
Sep. 30, 2012
Convertible Debt [Member]
Sep. 30, 2012
Convertible Debt [Member]
Mar. 31, 2012
Convertible Debt [Member]
Dec. 31, 2011
Convertible Debt [Member]
Earnings per share                    
Performance period to receive awards (in years)     3 years     3        
Common stock awards vesting multiplier, low end of range         0 0        
Common stock awards vesting multiplier, high end of range         2 2        
Interest rate on notes (as a percent)             3.50% 3.50%   3.50%
Stock Issued During Period, Shares, Conversion of Convertible Securities               864,106    
Debt Instrument, Principal Amount Denominator for Conversion into Common Stock             $ 1,000      
Common stock conversion price (in dollars per share)                 $ 54.42  
Calculation of basic and diluted earnings per share                    
Net income $ (38,336,000) $ 230,097,000 $ 12,889,000 $ 336,127,000            
Basic weighted-average common shares outstanding (in shares) 65,745,000 63,904,000 64,815,000 63,665,000            
Add: dilutive effect of stock options, unvested RSUs, and contingent PSAs (in shares) 0 2,062,000 1,870,000 2,589,000            
Add: dilutive effect of 3.50% Senior Convertible Notes (in shares) 0 1,420,000 658,000 1,136,000            
Diluted weighted-average common shares outstanding (in shares) 65,745,000 67,386,000 67,343,000 67,390,000            
Basic net income per common share (in dollars per share) $ (0.58) $ 3.60 $ 0.20 $ 5.28            
Diluted net income per common share (in dollars per share) $ (0.58) $ 3.41 $ 0.19 $ 4.99