Revenue Recognition (Summary Of Changes In Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revenue Recognition [Abstract]
Beginning balance	$ 107	$ 87
Commissions deferred, Current	138	128
Commission costs recognized, Current	(131)	(108)
Reclass to assets held for sale, Current	(9)
Ending balance	105	107
Beginning balance	127	117
Commissions deferred, Noncurrent	6	10
Reclass to assets held for sale, Noncurrent	(12)
Ending balance	$ 121	$ 127