Leases (Components of lease expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 240	$ 236	$ 232
Variable lease cost(1)	0	0	0
Sublease income	(1)	(4)	(3)
Total lease cost	239	232	229
Maximum [Member]
Lessee, Lease, Description [Line Items]
Variable lease cost(1)	$ 1	$ 1	$ 1