Supplemental Information (Narrative) (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Supplemental Information [Abstract]
Payables for purchased receivables	$ 34		$ 34		$ 33
Deferred Compensation Liability, Classified, Noncurrent	$ 78		$ 78		$ 80
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements (in shares)	1.6	2.1	1.5	1.8