Lease Obligations - Lessee - Lease Costs (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Lease Cost [Line Items]
Total finance lease costs		$ 14	$ 7
Total operating lease costs		137	124
Total lease costs		151	131
Net occupancy expense	[1]	350	332	$ 292
Impairment losses and termination charges		8	15
Occupancy
Lease Cost [Line Items]
Net occupancy expense				$ 101
Net occupancy and equipment expense
Lease Cost [Line Items]
Amortization of ROU assets		11	6
Interest on long-term debt
Lease Cost [Line Items]
Interest on lease liabilities		3	1
Net occupancy expense
Lease Cost [Line Items]
Operating lease cost		110	96
Short-term lease cost		1	1
Variable lease cost		29	30
Sublease income		$ (3)	$ (3)

[1] During the first quarter of 2020, certain noninterest income and noninterest expense line items were reclassified to better align disclosures to business activities. These reclassifications were retrospectively applied to all prior periods presented. Total noninterest income and noninterest expense did not change as a result of these reclassifications.