Fair Value Measurement (Unaudited) (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2015	Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Document Period End Date		Sep. 30, 2015
Derivatives:
Derivative assets		$ 116	$ 330
Derivatives:
Derivative Liability		74	99
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	25	23
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	4	11
Derivatives:
Derivative assets	[2],[5]	1	0
Total assets		30	34
Derivatives:
Derivative Liability	[2],[5]	7	6
Long-term debt, including current portion	[6]	0	0
Total liabilities		7	6
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	23	23
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	168	161
Derivatives:
Derivative assets	[2],[5]	17	15
Total assets		208	199
Derivatives:
Derivative Liability	[2],[5]	70	94
Long-term debt, including current portion	[6]	17,291	18,735
Total liabilities		17,361	18,829
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	0	0
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	0	0
Derivatives:
Derivative assets	[2],[5]	101	316
Total assets		101	316
Derivatives:
Derivative Liability	[2],[5]	0	0
Long-term debt, including current portion	[6]	0	0
Total liabilities		0	0
Fair Value, Measurements, Recurring [Member] | Embedded derivatives in provisional sales/purchases contracts [Member] | Fair Value, Inputs, Level 1 [Member]
Derivatives:
Derivative Liability	[2],[5]	0	0
Fair Value, Measurements, Recurring [Member] | Embedded derivatives in provisional sales/purchases contracts [Member] | Fair Value, Inputs, Level 2 [Member]
Derivatives:
Derivative Liability	[2],[5]	69	93
Fair Value, Measurements, Recurring [Member] | Embedded derivatives in provisional sales/purchases contracts [Member] | Fair Value, Inputs, Level 3 [Member]
Derivatives:
Derivative Liability	[2],[5]	0	0
Fair Value, Measurements, Recurring [Member] | Copper futures and swap contracts [Member] | Fair Value, Inputs, Level 1 [Member]
Derivatives:
Derivative Liability	[2],[5]	7	6
Fair Value, Measurements, Recurring [Member] | Copper futures and swap contracts [Member] | Fair Value, Inputs, Level 2 [Member]
Derivatives:
Derivative Liability	[2],[5]	1	1
Fair Value, Measurements, Recurring [Member] | Copper futures and swap contracts [Member] | Fair Value, Inputs, Level 3 [Member]
Derivatives:
Derivative Liability	[2],[5]	0	0
Fair Value, Measurements, Recurring [Member] | U.S. core fixed income fund [Member] | Fair Value, Inputs, Level 1 [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	0	0
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	0	0
Fair Value, Measurements, Recurring [Member] | U.S. core fixed income fund [Member] | Fair Value, Inputs, Level 2 [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	23	23
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	52	52
Fair Value, Measurements, Recurring [Member] | U.S. core fixed income fund [Member] | Fair Value, Inputs, Level 3 [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	0	0
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	0	0
Fair Value, Measurements, Recurring [Member] | Money market funds [Member] | Fair Value, Inputs, Level 1 [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	22	20
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	4	11
Fair Value, Measurements, Recurring [Member] | Money market funds [Member] | Fair Value, Inputs, Level 2 [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	0	0
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	0	0
Fair Value, Measurements, Recurring [Member] | Money market funds [Member] | Fair Value, Inputs, Level 3 [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	0	0
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	0	0
Fair Value, Measurements, Recurring [Member] | Collateralized mortgage-backed securities [Member] | Fair Value, Inputs, Level 1 [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	0	0
Fair Value, Measurements, Recurring [Member] | Collateralized mortgage-backed securities [Member] | Fair Value, Inputs, Level 2 [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	8	6
Fair Value, Measurements, Recurring [Member] | Collateralized mortgage-backed securities [Member] | Fair Value, Inputs, Level 3 [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	0	0
Fair Value, Measurements, Recurring [Member] | Equity securities [Member] | Fair Value, Inputs, Level 1 [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	3	3
Fair Value, Measurements, Recurring [Member] | Equity securities [Member] | Fair Value, Inputs, Level 2 [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	0	0
Fair Value, Measurements, Recurring [Member] | Equity securities [Member] | Fair Value, Inputs, Level 3 [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	0	0
Fair Value, Measurements, Recurring [Member] | Government bonds and notes [Member] | Fair Value, Inputs, Level 1 [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	0	0
Fair Value, Measurements, Recurring [Member] | Government bonds and notes [Member] | Fair Value, Inputs, Level 2 [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	41	39
Fair Value, Measurements, Recurring [Member] | Government bonds and notes [Member] | Fair Value, Inputs, Level 3 [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	0	0
Fair Value, Measurements, Recurring [Member] | Government mortgage-backed securities [Member] | Fair Value, Inputs, Level 1 [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	0	0
Fair Value, Measurements, Recurring [Member] | Government mortgage-backed securities [Member] | Fair Value, Inputs, Level 2 [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	28	19
Fair Value, Measurements, Recurring [Member] | Government mortgage-backed securities [Member] | Fair Value, Inputs, Level 3 [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	0	0
Fair Value, Measurements, Recurring [Member] | Corporate bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	0	0
Fair Value, Measurements, Recurring [Member] | Corporate bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	26	27
Fair Value, Measurements, Recurring [Member] | Corporate bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	0	0
Fair Value, Measurements, Recurring [Member] | Asset-backed securities [Member] | Fair Value, Inputs, Level 1 [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	0	0
Fair Value, Measurements, Recurring [Member] | Asset-backed securities [Member] | Fair Value, Inputs, Level 2 [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	12	17
Fair Value, Measurements, Recurring [Member] | Asset-backed securities [Member] | Fair Value, Inputs, Level 3 [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	0	0
Fair Value, Measurements, Recurring [Member] | Municipal bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	0	0
Fair Value, Measurements, Recurring [Member] | Municipal bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	1	1
Fair Value, Measurements, Recurring [Member] | Municipal bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	0	0
Fair Value, Measurements, Recurring [Member] | Embedded derivatives in provisional sales/purchases contracts [Member] | Fair Value, Inputs, Level 1 [Member]
Derivatives:
Derivative assets	[2],[5]	0	0
Fair Value, Measurements, Recurring [Member] | Embedded derivatives in provisional sales/purchases contracts [Member] | Fair Value, Inputs, Level 2 [Member]
Derivatives:
Derivative assets	[2],[5]	17	15
Fair Value, Measurements, Recurring [Member] | Embedded derivatives in provisional sales/purchases contracts [Member] | Fair Value, Inputs, Level 3 [Member]
Derivatives:
Derivative assets	[2],[5]	0	0
Fair Value, Measurements, Recurring [Member] | Crude oil options [Member] | Fair Value, Inputs, Level 1 [Member]
Derivatives:
Derivative assets	[2],[5]	0	0
Fair Value, Measurements, Recurring [Member] | Crude oil options [Member] | Fair Value, Inputs, Level 2 [Member]
Derivatives:
Derivative assets	[2],[5]	0	0
Fair Value, Measurements, Recurring [Member] | Crude oil options [Member] | Fair Value, Inputs, Level 3 [Member]
Derivatives:
Derivative assets	[2],[5]	101	316
Fair Value, Measurements, Recurring [Member] | Copper futures and swap contracts [Member] | Fair Value, Inputs, Level 1 [Member]
Derivatives:
Derivative assets	[2],[5]	1
Fair Value, Measurements, Recurring [Member] | Copper futures and swap contracts [Member] | Fair Value, Inputs, Level 2 [Member]
Derivatives:
Derivative assets	[2],[5]	0
Fair Value, Measurements, Recurring [Member] | Copper futures and swap contracts [Member] | Fair Value, Inputs, Level 3 [Member]
Derivatives:
Derivative assets	[2],[5]	0
Deferred Option Premiums and Accrued Interest [Member]
Derivatives:
Derivative Liability		53	210
Other Current Assets [Member]
Derivatives:
Derivative assets		101	316
Derivatives:
Derivative Liability		0	0
Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	48	46
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	172	172
Derivatives:
Derivative assets	[2],[5]	119	331
Derivatives:
Derivative Liability	[2],[5]	77	100
Long-term debt, including current portion	[6]	20,698	18,849
Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Embedded derivatives in provisional sales/purchases contracts [Member]
Derivatives:
Derivative Liability	[2],[5]	69	93
Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Copper futures and swap contracts [Member]
Derivatives:
Derivative Liability	[2],[5]	8	7
Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | U.S. core fixed income fund [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	23	23
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	52	52
Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Money market funds [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	22	20
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	4	11
Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Collateralized mortgage-backed securities [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	8	6
Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Equity securities [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	3	3
Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Government bonds and notes [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	41	39
Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Government mortgage-backed securities [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	28	19
Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Corporate bonds [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	26	27
Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Asset-backed securities [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	12	17
Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Municipal bonds [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	1	1
Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Embedded derivatives in provisional sales/purchases contracts [Member]
Derivatives:
Derivative assets	[2],[5]	17	15
Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Crude oil options [Member]
Derivatives:
Derivative assets	[2],[5]	101	316
Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Copper futures and swap contracts [Member]
Derivatives:
Derivative assets	[2],[5]	1
Reported Value Measurement [Member] | Other Current Assets [Member] | Fair Value, Measurements, Recurring [Member] | Time Deposits [Member]
Investment securities (current and long-term):
Investment securities		30	17
Reported Value Measurement [Member] | Other Assets [Member] | Fair Value, Measurements, Recurring [Member] | Time Deposits [Member]
Derivatives:
Escrow Deposit Disbursements Related to Property Acquisition		117	115
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	48	46
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	172	172
Derivatives:
Derivative assets	[2],[5]	119	331
Total assets		339	549
Derivatives:
Derivative Liability	[2],[5]	77	100
Long-term debt, including current portion	[6]	17,291	18,735
Total liabilities		17,368	18,835
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Embedded derivatives in provisional sales/purchases contracts [Member]
Derivatives:
Derivative Liability	[2],[5]	69	93
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Copper futures and swap contracts [Member]
Derivatives:
Derivative Liability	[2],[5]	8	7
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | U.S. core fixed income fund [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	23	23
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	52	52
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Money market funds [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	22	20
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	4	11
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Collateralized mortgage-backed securities [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	8	6
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Equity securities [Member]
Investment securities (current and long-term):
Investment securities	[1],[2]	3	3
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Government bonds and notes [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	41	39
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Government mortgage-backed securities [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	28	19
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Corporate bonds [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	26	27
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Asset-backed securities [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	12	17
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Municipal bonds [Member]
Legally restricted funds (long-term):
Legally restricted funds	[1],[2],[3],[4]	1	1
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Embedded derivatives in provisional sales/purchases contracts [Member]
Derivatives:
Derivative assets	[2],[5]	17	15
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Crude oil options [Member]
Derivatives:
Derivative assets	[2],[5]	101	316
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Copper futures and swap contracts [Member]
Derivatives:
Derivative assets	[2],[5]	1
Smelter Development [Member] | Reported Value Measurement [Member] | Other Current Assets [Member] | Fair Value, Measurements, Recurring [Member] | Time Deposits [Member]
Investment securities (current and long-term):
Investment securities		20
Reclamation Guarantee [Member] | Reported Value Measurement [Member] | Other Current Assets [Member] | Fair Value, Measurements, Recurring [Member] | Time Deposits [Member]
Investment securities (current and long-term):
Investment securities		$ 10	8
Customs Audit Assessment [Member] | Reported Value Measurement [Member] | Other Current Assets [Member] | Fair Value, Measurements, Recurring [Member] | Time Deposits [Member]
Investment securities (current and long-term):
Investment securities			$ 9

[1] Current portion included in other current assets and long-term portion included in other assets.

[2] Recorded at fair value.

[3] Excludes time deposits (which approximated fair value) included in other assets of $117 million at September 30, 2015, and $115 million at December 31, 2014, associated with an assurance bond to support PT-FI's commitment for smelter development in Indonesia.

[4] Excludes time deposits (which approximated fair value) included in other current assets of $30 million at September 30, 2015, associated with PT-FI's commitment for smelter development in Indonesia of $20 million and a reclamation guarantee at PT-FI of $10 million. Excludes time deposits of $17 million at December 31, 2014, associated with a customs audit assessment at PT-FI of $9 million and a reclamation guarantee at PT-FI of $8 million.

[5] Refer to Note 7 for further discussion and balance sheet classifications. Crude oil options are net of $53 million at September 30, 2015, and $210 million at December 31, 2014, for deferred premiums and accrued interest.

[6] Recorded at cost except for debt assumed in acquisitions, which were recorded at fair value at the respective acquisition dates.