Commitments, Contingencies and Other Items - Lawsuits (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013
Loss Contingencies
Estimated Litigation Liability	$ 275
Peruvian Tax Litigation | Pending Litigation
Loss Contingencies
Loss Contingency, Asserted Claim	96
Peruvian Tax Litigation, Before Interest | Pending Litigation
Loss Contingencies
Loss Contingency, Asserted Claim	26
Peruvian Tax Litigation, Income Taxwitholding 2001 and 2002 | Pending Litigation
Loss Contingencies
Loss Contingency, Asserted Claim	3
Peruvian Tax Litigation, Disallowance of VAT in 2005 | Pending Litigation
Loss Contingencies
Loss Contingency, Asserted Claim	16
Peruvian Tax Litigation, VAT for 2001 and 2002 | Pending Litigation
Loss Contingencies
Loss Contingency, Asserted Claim	7
Employee Severance and Contractor Termination Disputes | Pending Litigation
Loss Contingencies
Loss Contingency, Asserted Claim	40
up to | Brazilian Tax Claims | Pending Litigation
Loss Contingencies
Loss Contingency, Range of Possible Loss, Portion Not Accrued	$ 61