Financial Instruments (Unrealized gains losses) (Details) oz in Thousands, lb in Millions, $ in Millions	1 Months Ended	3 Months Ended
	Apr. 30, 2020 lb $ / lb	Mar. 31, 2020 USD ($) lb oz $ / lb $ / lb $ / oz	Mar. 31, 2019 USD ($)
Not Designated as Hedging Instrument [Member] | Amounts recorded in Sales [Member]
Realized gains (losses):
Embedded Derivative, Gain (Loss) on Embedded Derivative, Net | $		$ (231)	$ 120
Commodity Contract [Member]
Unrealized gains (losses):
Derivative financial instruments | $		(33)	18
Hedged item – firm sales commitments | $		33	(18)
Realized gains (losses):
Matured derivative financial instruments | $		$ (9)	2
Commodity Contract [Member] | Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | lb		84
Derivative, Average Forward Price | $ / lb		2.56
Copper Forward Contracts [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | lb		34
Derivative, Average Forward Price | $ / lb		2.35
Copper Forward Contracts [Member] | Not Designated as Hedging Instrument [Member] | Amounts recorded in Cost of Sales
Realized gains (losses):
Matured derivative financial instruments | $		$ 24	1
Copper | Not Designated as Hedging Instrument [Member] | Amounts recorded in Sales [Member]
Realized gains (losses):
Embedded Derivative, Gain (Loss) on Embedded Derivative, Net | $		$ (238)	122
Copper | Short [Member] | Embedded Derivative Financial Instruments [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | lb		333
Derivative, Average Forward Price | $ / lb		2.59
Realized gains (losses):
Derivative Average Market Price | $ / lb		2.24
Copper | Long [Member] | Embedded Derivative Financial Instruments [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | lb		87
Derivative, Average Forward Price | $ / lb		2.58
Realized gains (losses):
Derivative Average Market Price | $ / lb		2.24
Gold | Short [Member] | Embedded Derivative Financial Instruments [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | oz		92
Derivative, Average Forward Price | $ / oz		1,601
Realized gains (losses):
Derivative Average Market Price | $ / oz		1,614
gold and other | Not Designated as Hedging Instrument [Member] | Amounts recorded in Sales [Member]
Realized gains (losses):
Embedded Derivative, Gain (Loss) on Embedded Derivative, Net | $		$ 7	$ (2)
Subsequent event | Copper Forward Contracts [Member] | Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | lb	150
Derivative, Average Forward Price | $ / lb	2.34