Financial Instruments (Unrealized gains losses) (Details) oz in Thousands, lb in Millions, $ in Millions		3 Months Ended		6 Months Ended
	Jun. 30, 2017 lb oz $ / lb $ / lb $ / oz	Jun. 30, 2017 USD ($) $ / lb $ / lb $ / oz	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) $ / lb $ / lb $ / oz	Jun. 30, 2016 USD ($)
Commodity Contract [Member]
Unrealized gains (losses):
Derivative financial instruments | $		$ 1	$ 3	$ (1)	$ 10
Hedged item – firm sales commitments | $		(1)	(3)	1	(10)
Realized gains (losses):
Matured derivative financial instruments | $		$ 1	(4)	$ 9	(8)
Commodity Contract [Member] | Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | lb	49
Derivative, Average Forward Price	2.59	2.59		2.59
Embedded Derivative Financial Instruments [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Amounts recorded in Sales [Member]
Realized gains (losses):
Matured derivative financial instruments | $		$ 34	4	$ 160	76
Copper Forward Contracts [Member] | Derivatives Not Designated as Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | lb	33
Derivative, Average Forward Price	2.57	2.57		2.57
Copper Forward Contracts [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Amounts recorded in Cost of Sales
Realized gains (losses):
Matured derivative financial instruments | $		$ (4)	$ (2)	$ (5)	$ 5
Copper | Short [Member] | Embedded Derivative Financial Instruments [Member] | Derivatives Not Designated as Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | lb	560
Derivative, Average Forward Price	2.58	2.58		2.58
Realized gains (losses):
Derivative Average Market Price	2.69	2.69		2.69
Copper | Long [Member] | Embedded Derivative Financial Instruments [Member] | Derivatives Not Designated as Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | lb	109
Derivative, Average Forward Price	2.60	2.60		2.60
Realized gains (losses):
Derivative Average Market Price	2.69	2.69		2.69
Gold | Short [Member] | Embedded Derivative Financial Instruments [Member] | Derivatives Not Designated as Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | oz	165
Derivative, Average Forward Price | $ / oz	1,259	1,259		1,259
Realized gains (losses):
Derivative Average Market Price | $ / oz	1,245	1,245		1,245