XML 68 R65.htm IDEA: XBRL DOCUMENT v2.4.0.6
BENEFIT PLANS: (Details 2) (USD $)
In Millions, except Per Share data, unless otherwise specified
 12 Months Ended
Dec. 31, 2012
Y
class
Dec. 31, 2011
Dec. 31, 2010
Post retirement defined benefit plan | Peruvian operations
      
Benefit plans      
Net asset value (in dollars per share) $ 1.00    
Target duration of funds invested in publicly traded, investment grade securities (in years) 1.5    
Percentage of total assets, the Money Fund intends to invest in bank obligations under normal market conditions 25.00%    
Maturity period of 4% coupon on which Bond Fund has an underweight position (in years) 30    
Interest rate of coupon on which Bond Fund has an underweight position (as a percentage) 4.00%    
Maturity period of 4.5% coupon on which Bond Fund has an overweight position (in years) 30    
Interest rate of coupon on which Bond Fund is overweight (as a percent) 4.50%    
Interest rate of coupon one on which Bond Fund moved from very overweight to neutral position (as a percent) 3.00%    
Interest rate of coupon two on which Bond Fund moved from very overweight to neutral position (as a percent) 3.50%    
Number of classes of grades in which Blackrock has switched its exposure 2    
Assumptions used to determine the pension obligation and seniority premiums as of year-end and the net cost in the ensuing year      
Discount rate (as a percent) 3.35% 3.95% 5.00%
Expected long-term rate of return on plan asset (as a percent) 4.50% 4.50% 4.50%
Asset allocation (as a percent) 100.00% 100.00%  
Post retirement defined benefit plan | Mexican operations
      
Assumptions used to determine the pension obligation and seniority premiums as of year-end and the net cost in the ensuing year      
Discount rate (as a percent) 6.50% 7.50% 7.50%
Expected long-term rate of return on plan asset (as a percent) 6.50% 7.50% 7.50%
Number of financial institutions managing plan assets 3    
Plan obligations as a percentage of benefit obligation 30.00%    
Expected employer contribution in next fiscal year $ 8.6    
Pending payments to former Buenavista workers $ 3.4    
Post retirement defined benefit plan | Minimum | Peruvian operations
      
Benefit plans      
Period of Bond Fund for which interest rate or yield curve position was overweight 7    
Percentage of underweight versus the benchmark due to BlackRock's reduced exposure to agency mortgages 2.00%    
Post retirement defined benefit plan | Maximum | Peruvian operations
      
Benefit plans      
Period of Bond Fund for which interest rate or yield curve position was overweight 10    
Percentage of underweight versus the benchmark due to BlackRock's reduced exposure to agency mortgages 3.00%    
Post retirement defined benefit plan | Parent Company (Grupo Mexico) common shares | Mexican operations
      
Assumptions used to determine the pension obligation and seniority premiums as of year-end and the net cost in the ensuing year      
Asset allocation (as a percent) 73.00%    
Post retirement defined benefit plan | Equity securities | Mexican operations
      
Assumptions used to determine the pension obligation and seniority premiums as of year-end and the net cost in the ensuing year      
Asset allocation (as a percent) 73.00% 74.00%  
Post retirement defined benefit plan | Treasury bills | Mexican operations
      
Assumptions used to determine the pension obligation and seniority premiums as of year-end and the net cost in the ensuing year      
Asset allocation (as a percent) 27.00% 26.00%  
Post-retirement Health Care Plan | Peruvian operations
      
Assumptions used to determine the pension obligation and seniority premiums as of year-end and the net cost in the ensuing year      
Discount rate (as a percent) 3.35% 3.95% 5.00%