Other Assets - Intangible Assets Disclosure (Detail) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	$ 2,072	$ 2,188
Accumulated amortization	(1,549)	(1,558)
Net carrying value	523	630
Customer Lists [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	1,472	1,478
Accumulated amortization	(1,112)	(1,089)
Net carrying value	360	389
Acquired leases and other [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	600	710
Accumulated amortization	(437)	(469)
Net carrying value	$ 163	$ 241