New Accounting Standard - Leases Presented in Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2019	Jan. 01, 2019
Assets and Liabilities, Lessee [Abstract]
Lease right-of-use assets (included in property, plant, equipment and mine development costs, net)	$ 241	$ 243
Short-term lease liabilities (included in accounts payable and accrued liabilities)	45
Long-term lease liabilities (included in other liabilities)	211
Total lease liabilities	$ 256	$ 243