Pension and Other Employee Benefits (Schedule of Change in Plan Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Pension Plan [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Fair value of plan assets at beginning of year	$ 19,321	$ 21,002
Actual return (loss) on plan assets	3,516	(775)
Company contributions	343	2,139
Plan participants’ contributions	4	6
Plan settlements	(7)	(474)
Foreign exchange gain (loss)	20	(50)
Benefits paid	(1,880)	(2,527)
Fair value of plan assets at end of year	21,317	19,321
PRB [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Fair value of plan assets at beginning of year	300	358
Actual return (loss) on plan assets	50	(14)
Company contributions	37	22
Plan participants’ contributions	58	49
Plan settlements	(9)	(10)
Foreign exchange gain (loss)	0	0
Benefits paid	(112)	(105)
Fair value of plan assets at end of year	$ 324	$ 300