Other Assets - Intangible Assets Disclosure (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	$ 2,163	$ 2,217
Accumulated amortization	(1,531)	(1,576)
Net carrying value	632	641
Customer Lists [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	1,478	1,427
Accumulated amortization	(1,078)	(1,044)
Net carrying value	400	383
Acquired leases and other [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	685	790
Accumulated amortization	(453)	(532)
Net carrying value	$ 232	$ 258