Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation and Cash-Based Incentive Compensation (Schedule of Stock Activity Related to Share-Based Compensation) (Parenthetical) (Detail)

v2.4.0.6
Share-Based Compensation and Cash-Based Incentive Compensation (Schedule of Stock Activity Related to Share-Based Compensation) (Parenthetical) (Detail)
 9 Months Ended
Sep. 30, 2012
Restricted Stock [Member] | Current Year [Member]
  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Awards expected to vest by period 2,662
Restricted Stock [Member] | 2013 [Member]
  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Awards expected to vest by period 24,019
Restricted Stock [Member] | 2014 [Member]
  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Awards expected to vest by period 12,354
Restricted Stock [Member] | 2015 [Member]
  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Awards expected to vest by period 7,314
Restricted Stock Units (RSUs) [Member] | Current Year [Member]
  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Awards expected to vest by period 1,198,208
Restricted Stock Units (RSUs) [Member] | 2013 [Member]
  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Awards expected to vest by period 493,716
Restricted Stock Units (RSUs) [Member] | 2014 [Member]
  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Awards expected to vest by period 752,058
Restricted stock units expected to increase 864,867
Minimum [Member]
  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Range of Restricted stock units 0
Maximum [Member]
  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Range of Restricted stock units 864,867