Parent Company Financial Information - Statements of Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for loan losses
Other assets	$ 4,072	$ 2,297
Total assets	84,209	43,311
Liabilities and equity:
Term borrowings	1,670	791
Total liabilities	75,902	38,235
Total equity	8,307	5,076	$ 4,786	$ 4,581
Total liabilities and equity	84,209	43,311
Parent Company
Assets:
Cash	827	369
Notes receivable	3	3
Allowance for loan losses
Bank	8,176	5,039
Non-bank	88	18
Other assets	274	171
Total assets	9,368	5,600
Liabilities and equity:
Accrued employee benefits and other liabilities	322	177
Term borrowings	1,034	642
Total liabilities	1,356	819
Total equity	8,012	4,781
Total liabilities and equity	$ 9,368	$ 5,600