Share-based Compensation (Details 2) (USD $)
3 Months Ended 6 Months Ended 3 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
year
Jun. 30, 2011
Jun. 30, 2012
Restricted Stock Units
Mar. 31, 2012
Restricted Stock Units
Restricted Stock information            
Restricted stock units (RSUs) granted in period (in shares)         350,500 1,066,567
Vesting subject to the grantees continued employment or providing service (in shares)           550,000
Vesting subject to the grantees continued employment or providing service and certain performance and market conditions (in shares)           516,567
Fair value of restricted stock granted during the period         $ 3,600,000 $ 14,700,000
Vesting period           3 years
Recognized compensation costs 4,906,000 1,916,000 9,377,000 3,210,000    
Unrecognized compensation costs related to unvested options and RSUs $ 32,700,000   $ 32,700,000      
Weighted average remaining vesting period for recognition of compensation costs (in years)     2.6