Fair Value Measurements And Disclosure (Fair Value Leveling) (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Domestic Equities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities		$ 1,215	$ 1,132
Domestic Equities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities		1,215	1,132
Domestic Equities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities		0	0
Domestic Equities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities		0	0
International Equities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities		594	569
International Equities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities		594	569
International Equities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities		0	0
International Equities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities		0	0
Fixed Income Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities		508	680
Fixed Income Bonds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities		0	0
Fixed Income Bonds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities		508	680
Fixed Income Bonds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities		0	0
Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Derivatives	[1]	79	136
Liability Derivatives	[1]	(14)
Interest Rate Swaps [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Derivatives	[1]	0	0
Liability Derivatives	[1]	0
Interest Rate Swaps [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Derivatives	[1]	79	136
Liability Derivatives	[1]	(14)
Interest Rate Swaps [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Derivatives	[1]	0	0
Liability Derivatives	[1]	0
Cross-Currency Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Derivatives	[1]	89	556
Liability Derivatives	[1]	(3,867)	(3,466)
Cross-Currency Swaps [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Derivatives	[1]	0	0
Liability Derivatives	[1]	0	0
Cross-Currency Swaps [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Derivatives	[1]	89	556
Liability Derivatives	[1]	(3,867)	(3,466)
Cross-Currency Swaps [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Derivatives	[1]	0	0
Liability Derivatives	[1]	$ 0	0
Foreign Exchange Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Derivatives	[1]		3
Foreign Exchange Contracts [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Derivatives	[1]		0
Foreign Exchange Contracts [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Derivatives	[1]		3
Foreign Exchange Contracts [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Derivatives	[1]		$ 0

[1] Derivatives designated as hedging instruments are reflected as "Other assets," "Other noncurrent liabilities" and, for a portion of interest rate swaps, "Other current assets" on our consolidated balance sheets.