Debt (Schedule of Long-term Debt) (Details) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016	Jul. 15, 2016
Long-Term Debt
Subtotal		$ 2,905	$ 2,938
Current installments of long-term debt		(34)	(27)
Total		2,851	2,890
Long-term Debt [Member]
Long-Term Debt
Unamortized debt issuance costs	[1]	(20)	(21)
Senior Unsecured Term Loan Due 2021 [Member]
Long-Term Debt
Senior unsecured debt	[2]	$ 500	500	$ 500
Date of maturity		Jul. 15, 2021
Senior Unsecured Notes Due 2019 [Member]
Long-Term Debt
Senior unsecured debt		$ 321	316
Interest rate		3.25%
Date of maturity		Oct. 15, 2019
Senior Unsecured Notes Due 2021 [Member]
Long-Term Debt
Senior unsecured debt		$ 400	400
Interest rate		5.875%
Date of maturity		Jun. 15, 2021
Senior Unsecured Notes Due 2022 [Member]
Long-Term Debt
Senior unsecured debt		$ 500	500
Interest rate		4.625%
Date of maturity		Nov. 15, 2022
Senior Unsecured Notes Due 2023 [Member]
Long-Term Debt
Senior unsecured debt		$ 800	788
Interest rate		1.125%
Date of maturity		Sep. 26, 2023
Refunding loan for pollution control and industrial revenue bonds [Member]
Long-Term Debt
Other long-term debt		$ 169	$ 170
Date of maturity		Dec. 31, 2030
Bank Loans Acquired from SOFTER [Member]
Debt Instrument [Line Items]
Long-term Debt, Weighted Average Interest Rate			1.60%
Long-Term Debt
Other long-term debt	[3]	$ 0	$ 47
Date of maturity		Dec. 31, 2021
Obligations Under Capital Leases [Member]
Long-Term Debt
Capital lease obligations		$ 215	$ 217
Date of maturity		Dec. 31, 2054
Minimum [Member] | Refunding loan for pollution control and industrial revenue bonds [Member]
Long-Term Debt
Interest rate		4.05%
Maximum [Member] | Refunding loan for pollution control and industrial revenue bonds [Member]
Long-Term Debt
Interest rate		5.00%
London Interbank Offered Rate (LIBOR) [Member] | Senior Unsecured Term Loan Due 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.50%

[1] Related to the Company's long-term debt, excluding obligations under capital leases.

[2] The margin for borrowings under the senior unsecured term loan due 2021 was 1.5% above LIBOR at current Company credit ratings.

[3] The weighted average interest rate was 1.6% as of December 31, 2016.