Revenue Recognition (Summary Of Changes In Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Revenue Recognition [Abstract]
Beginning balance	$ 105	$ 107
Commissions deferred, Current	94	138
Commission costs recognized, Current	(116)	(131)
Reclass to assets held for sale, Current		(9)
Reclassified between Current and Noncurrent, Current	14
Ending balance	97	105
Beginning balance	121	127
Commissions deferred, Noncurrent	13	6
Commission costs recognized, Noncurrent	(4)
Reclass to assets held for sale, Noncurrent		(12)
Reclassified between Current and Noncurrent, Noncurrent	(14)
Ending balance	$ 116	$ 121