Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2017

Fair Value Disclosures [Abstract]

Carrying and Estimated Fair Value

The net carrying and estimated fair values of our financial instruments by class at March 31, 2017 and December 31, 2016 were as follows:

	March 31, 2017				December 31, 2016
	Net Carrying Amount		Fair Value		Net Carrying Amount		Fair Value
	(Millions)
Long-term debt (including current maturities)	$	1,409	$	1,418	$	1,297	$	1,311
Instruments with off-balance sheet risk:
Foreign exchange forward contracts:
Asset derivative contracts	—		—		—		—

Summarization for Foreign Currency Forward Purchase and Sale Contracts

The following table summarizes by major currency the notional amounts for foreign currency forward purchase and sale contracts as of March 31, 2017 (all of which mature in 2017):

		Notional Amount in Foreign Currency
		(Millions)
British pounds	—Purchase	19
	—Sell	(9	)
Canadian dollars	—Purchase	2
	—Sell	(4	)
European euro	—Purchase	10
	—Sell	(5	)
Japanese yen	—Purchase	89
	—Sell	(90	)
South African rand	—Sell	(7	)
U.S. dollars	—Purchase	21
	—Sell	(35	)