Leases - Components of Operating Lease Costs (Details) $ in Millions		12 Months Ended
		Dec. 31, 2020 USD ($) branch	Dec. 31, 2019 USD ($) branch
Lessee, Lease, Description [Line Items]
Operating lease cost		$ 127	$ 136
Variable lease cost		59	63
Short-term lease cost		0	4
Sublease income	[1]	(54)	(60)
Total operating lease costs, net		132	143
Cash paid for amounts included in the measurement of operating lease liabilities		135	126
ROU assets recognized for new operating lease liabilities		24	132
Impairment charge		$ 76	$ 13
Number of branches closing | branch		60	20

[1] We have entered into agreements to sublease certain office space, including agreements to receive rental income from our affiliates for rent. As owner or lessee of the properties, we have entered into agreements with these affiliates to charge them rent based on the office space utilized by their employees during the period. See Note 23, "Related Party Transactions," for further disclosure