Pension and Other Employee Benefits (Schedule of Fair Value Measurements of the Company's Pension Plan Assets By Asset Category And By Level) (Details) - UNITED STATES - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 20,366	$ 18,488
Level 1 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	6,113	7,206
Level 2 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	2,511	2,288
Level 3 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	32	31
Not subject to leveling(7)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	11,710	8,963
U.S. equities(1)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	5,563	4,701
U.S. equities(1) | Level 1 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	715	2,189
U.S. equities(1) | Level 2 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
U.S. equities(1) | Level 3 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
U.S. equities(1) | Not subject to leveling(7)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	4,848	2,512
International equities(1)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	3,403	3,141
International equities(1) | Level 1 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	2,838	2,522
International equities(1) | Level 2 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	13	4
International equities(1) | Level 3 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
International equities(1) | Not subject to leveling(7)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	552	615
Real assets(2)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	157	53
Real assets(2) | Level 1 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Real assets(2) | Level 2 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Real assets(2) | Level 3 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Real assets(2) | Not subject to leveling(7)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	157	53
U.S. government and agency securities
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	2,026	1,923
U.S. government and agency securities | Level 1 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	1,836	1,727
U.S. government and agency securities | Level 2 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	190	196
U.S. government and agency securities | Level 3 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
U.S. government and agency securities | Not subject to leveling(7)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Corporate debt securities/instruments(3)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	3,039	2,907
Corporate debt securities/instruments(3) | Level 1 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	378	329
Corporate debt securities/instruments(3) | Level 2 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	2,308	2,088
Corporate debt securities/instruments(3) | Level 3 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Corporate debt securities/instruments(3) | Not subject to leveling(7)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	353	490
Global multi-sector fixed income(4)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	303	400
Global multi-sector fixed income(4) | Level 1 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	303	400
Global multi-sector fixed income(4) | Level 2 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Global multi-sector fixed income(4) | Level 3 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Global multi-sector fixed income(4) | Not subject to leveling(7)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Securitized and structured credit(5)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	573	534
Securitized and structured credit(5) | Level 1 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Securitized and structured credit(5) | Level 2 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Securitized and structured credit(5) | Level 3 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Securitized and structured credit(5) | Not subject to leveling(7)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	573	534
Cash and cash equivalents(6)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	603	486
Cash and cash equivalents(6) | Level 1 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	43	39
Cash and cash equivalents(6) | Level 2 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Cash and cash equivalents(6) | Level 3 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Cash and cash equivalents(6) | Not subject to leveling(7)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	560	447
Absolute return funds
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	1,564	1,432
Absolute return funds | Level 1 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Absolute return funds | Level 2 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Absolute return funds | Level 3 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Absolute return funds | Not subject to leveling(7)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	1,564	1,432
Private equity funds
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	1,579	1,419
Private equity funds | Level 1 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Private equity funds | Level 2 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Private equity funds | Level 3 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Private equity funds | Not subject to leveling(7)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	1,579	1,419
Private real estate funds
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	1,403	1,264
Private real estate funds | Level 1 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Private real estate funds | Level 2 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Private real estate funds | Level 3 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Private real estate funds | Not subject to leveling(7)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	1,403	1,264
Insurance contracts
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	32	31
Insurance contracts | Level 1 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Insurance contracts | Level 2 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Insurance contracts | Level 3 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	32	31
Insurance contracts | Not subject to leveling(7)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Total investments
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	20,245	18,291
Total investments | Level 1 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	6,113	7,206
Total investments | Level 2 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	2,511	2,288
Total investments | Level 3 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	32	31
Total investments | Not subject to leveling(7)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	11,589	8,766
Net receivables and payables
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	121	197
Net receivables and payables | Level 1 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Net receivables and payables | Level 2 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Net receivables and payables | Level 3 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Net receivables and payables | Not subject to leveling(7)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 121	$ 197