XML 96 R66.htm IDEA: XBRL DOCUMENT v2.4.0.6
BENEFIT PLANS: (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
BENEFIT PLANS:      
Number of Peruvian noncontributory defined benefit pension plans 2    
Defined contribution plan      
Matching employer contribution as a percentage of participating employee's base salary for Minera Mexico salaried employees 3.00%    
Contribution expense $ 1.0 $ 0.9  
Defined contribution plan liability 1.4 1.8  
Peru Defined Benefit Pension Plans
      
Defined benefit plan, net periodic benefit cost      
Interest cost 0.6 0.6 0.7
Expected return on plan assets (0.7) (0.7) (0.6)
Amortization of net loss (gain) 0.1 0.1 0.1
Net periodic benefit costs     0.2
Amortization of net (loss) gain 0.1 0.1  
Change in benefit obligation:      
Projected benefit obligation at beginning of year 12.5 12.1  
Interest cost 0.6 0.6 0.7
Benefits paid (0.1) (0.9)  
Actuarial gain census 0.2 0.1  
Actuarial gain assumption changes 1.3 0.6  
Projected benefit obligation at end of year 13.6 12.5 12.1
Change in plan assets:      
Fair value of plan assets at beginning of year 16.6 16.5  
Actual return on plan assets 1.1 0.1  
Benefits paid (0.9) (0.9)  
Fair value of plan assets at end of year 16.8 16.6 16.5
Funded status at end of year 3.2 4.1  
Amounts recognized in statement of financial position      
Non-current assets 3.2 4.1  
Total 3.2 4.1  
Amounts recognized in accumulated other comprehensive income      
Net loss net of income tax 3.1 2.5  
Total, net of tax (3.1) (2.5) (2.3)
Tax effect of amounts recognized in accumulated other comprehensive income 1.7 1.3  
Reconciliation of accumulated other comprehensive income:      
Accumulated other comprehensive income at beginning of plan year 2.5 2.3  
Net loss / (gain) occurring during the year 0.7 0.2  
Amortization of net loss (gain) (0.1)    
Net adjustment to accumulated other comprehensive income (0.6) (0.2)  
Accumulated other comprehensive income at end of plan year 3.1 2.5 2.3
Maximum net loss/ (gain) occurring during the year 0.1 0.1  
Amounts in accumulative other comprehensive income amortized and recognized as a component of net periodic benefit cost, net of income tax      
Net loss / (gain) 0.7 0.2  
Amortization of net (loss) gain 0.1    
Total amortization expenses 0.6 0.2  
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) 3.95% 3.95% 5.55%
Expected long-term rate of return on plan asset (as a percent) 4.50% 4.50% 4.50%
Expected Benefit Payments      
2012 1.0    
2013 0.9    
2014 1.0    
2015 0.9    
2016 0.9    
2017 to 2020 4.6    
Total 9.3    
Peru Post-retirement Health Care Plan
      
Defined benefit plan, net periodic benefit cost      
Interest cost 0.1 0.1 0.1
Net periodic benefit costs 0.1 0.1 0.1
Change in benefit obligation:      
Projected benefit obligation at beginning of year 1.7 2.0  
Interest cost 0.1 0.1 0.1
Benefits paid (0.1) (0.2)  
Actuarial gain assumption changes 0.2 0.1  
Actuarial gain (loss) - claims cost   (0.3)  
Projected benefit obligation at end of year 1.9 1.7 2.0
Change in plan assets:      
Employer contribution 0.1 0.1  
Benefits paid (0.1) (0.1)  
Funded status at end of year (1.9) (1.7)  
Amounts recognized in statement of financial position      
Current liabilities (0.1) (0.1)  
Non-current liabilities (1.8) (1.6)  
Total (1.9) (1.7)  
Amounts recognized in accumulated other comprehensive income      
Net loss net of income tax 0.6 0.5  
Prior service cost (credit) (0.1) (0.1)  
Total, net of tax (0.5) (0.4) (0.5)
Reconciliation of accumulated other comprehensive income:      
Accumulated other comprehensive income at beginning of plan year 0.4 0.5  
Net loss / (gain) occurring during the year 0.1 (0.1)  
Net adjustment to accumulated other comprehensive income 0.1 (0.1)  
Accumulated other comprehensive income at end of plan year 0.5 0.4 0.5
Amounts in accumulative other comprehensive income amortized and recognized as a component of net periodic benefit cost, net of income tax      
Net loss / (gain) (0.1) 0.1  
Total amortization expenses (0.1) 0.1  
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) 3.95% 5.00%  
Expected Benefit Payments      
2012 0.1    
2013 0.1    
2014 0.1    
2015 0.1    
2016 0.1    
2017 to 2020 0.6    
Total 1.1    
Assumed trend rate for covered health care benefit cost (as a percent) 6.00%    
Assumed ultimate trend rate for health care benefit cost (as a percent) 4.50%    
Peru Post-retirement Health Care Plan | Maximum
      
Defined benefit plan, net periodic benefit cost      
Amortization of net loss (gain) 0.1 0.1 0.1
Amortization of prior services cost/ (credit) 0.1 0.1 0.1
Minera Mexico Defined Benefit Pension Plans
      
Defined benefit plan, net periodic benefit cost      
Interest cost 0.6 1.6 1.5
Expected return on plan assets (2.8) (3.0) (2.2)
Amortization of net loss (gain) 1.3 1.0 0.1
Service cost 0.9 2.1 1.8
Amortization of prior services cost/ (credit)   0.2 0.2
Amortization of transition assets, net (0.1)   (0.1)
Settlement/curtailment   (19.0)  
Net periodic benefit costs (2.7) (19.1) 1.1
Change in benefit obligation:      
Projected benefit obligation at beginning of year 12.7 32.5  
Interest cost 0.6 1.6 1.5
Benefits paid (0.9) (0.9)  
Actuarial gain assumption changes (0.4) (0.6)  
Service cost 0.9 2.1 1.8
Settlement/curtailment   (23.7)  
Inflation adjustment (1.3) 1.7  
Projected benefit obligation at end of year 11.6 12.7 32.5
Severance to Buenavista workers   11.9  
Change in plan assets:      
Fair value of plan assets at beginning of year 46.3 38.8  
Currency exchange rate adjustment (5.4) 2.1  
Actual return on plan assets (1.1) 6.9  
Employer contribution (0.5) (0.6)  
Benefits paid (0.2) (0.9)  
Fair value of plan assets at end of year 39.1 46.3 38.8
Funded status at end of year 27.5 33.6  
Amounts recognized in statement of financial position      
Non-current assets 27.5 33.6  
Total 27.5 33.6  
Amounts recognized in accumulated other comprehensive income      
Net loss net of income tax (7.0) (11.2)  
Transition obligation (asset)   (0.1)  
Total, net of tax 7.0 11.3 6.1
Tax effect of amounts recognized in accumulated other comprehensive income 4.7 7.6  
Reconciliation of accumulated other comprehensive income:      
Accumulated other comprehensive income at beginning of plan year (11.3) (6.1)  
Net loss / (gain) occurring during the year 2.2 (2.7)  
Amortization of net loss (gain) 0.8 0.6  
Prior services cost amortized during the year   (0.1)  
Settlement/curtailment   (2.8)  
Currency exchange rate changes 1.3 (0.2)  
Net adjustment to accumulated other comprehensive income 4.3 (5.2)  
Accumulated other comprehensive income at end of plan year (7.0) (11.3) (6.1)
Amounts in accumulative other comprehensive income amortized and recognized as a component of net periodic benefit cost, net of income tax      
Amortization of net (loss) gain 0.8 0.6  
Amortization of prior service cost (credit)   (0.1)  
Total amortization expenses 0.8 0.5  
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) 7.50% 7.50% 8.00%
Expected long-term rate of return on plan asset (as a percent) 7.50% 7.50% 8.00%
Rate of increase in future compensation level (as a percent) 4.50% 4.00% 0.00%
Expected Benefit Payments      
2012 7.3    
2013 0.5    
2014 0.5    
2015 0.5    
2016 0.5    
2017 to 2020 3.4    
Total 12.7    
Minera Mexico Post-retirement health care plan
      
Defined benefit plan, net periodic benefit cost      
Interest cost 3.2 4.3 4.3
Amortization of net loss (gain)   0.1 0.5
Service cost   0.4 0.4
Amortization of prior services cost/ (credit) (10.0)    
Amortization of transition assets, net 1.3 1.5 1.5
Net periodic benefit costs (5.5) 6.3 6.7
Change in benefit obligation:      
Projected benefit obligation at beginning of year 49.7 53.0  
Interest cost 3.2 4.3 4.3
Actuarial gain assumption changes (3.3) (11.1)  
Service cost   0.4 0.4
Amendments (24.2)    
Currency exchange rate adjustment (5.7) 3.1  
Projected benefit obligation at end of year 18.4 49.7 53.0
Change in plan assets:      
Benefits paid (1.3)    
Funded status at end of year (18.4) (49.7)  
Amounts recognized in statement of financial position      
Non-current liabilities (18.4) (49.7)  
Total (18.4) (49.7)  
Amounts recognized in accumulated other comprehensive income      
Net loss net of income tax (4.0) (2.3)  
Prior service cost (credit) 14.5    
Transition obligation (asset)   10.5  
Total, net of tax 4.0 (8.2) (15.5)
Tax effect of amounts recognized in accumulated other comprehensive income (2.7) 5.5  
Reconciliation of accumulated other comprehensive income:      
Accumulated other comprehensive income at beginning of plan year 8.2 15.5  
Net loss / (gain) occurring during the year (2.0) (6.7)  
Amortization of net loss (gain)   (0.1)  
Transition obligation (asset) (0.8) (0.9)  
Prior services cost amortized during the year 6.0    
Currency exchange rate changes (0.9) 0.4  
Net adjustment to accumulated other comprehensive income (12.2) (7.3)  
Accumulated other comprehensive income at end of plan year (4.0) 8.2 15.5
Amounts in accumulative other comprehensive income amortized and recognized as a component of net periodic benefit cost, net of income tax      
Amortization of net (loss) gain   0.1  
Transition obligation (asset) (0.8) (0.9)  
Amortization of prior service cost (credit) (6.0)    
Total amortization expenses (5.2) 1.0  
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) 7.50% 7.50%  
Expected Benefit Payments      
2012 1.4    
2013 1.5    
2014 1.6    
2015 1.7    
2016 1.8    
2017 to 2020 13.0    
Total 21.0    
Assumed trend rate for covered health care benefit cost (as a percent) 4.50%    
Effect of one percentage-point change in assumed other benefit cost trend rates      
Effect of one percentage-point increase on total service and interest cost components 1.5    
Effect of one percentage-point decrease on total service and interest cost components 1.2    
Effect of one percentage-point increase on post-retirement benefit obligation 20.2    
Effect of one percentage-point decrease on post-retirement benefit obligation $ 16.8