Loans Held for Sale - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	$ 282		$ 282		$ 289
Revenue associated with the economic hedging program (less than)	276	$ 189	(22)	$ 1,738
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	193		193		212
Valuation allowance	17		17		0
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	89		89		77
Valuation allowance	0		0		2
Commercial Loans - Fair Value Option [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	41		41		178
Commercial Loans - Transferred to Held for Sale [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	152		152		34
Residential Mortgage [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	89		89		$ 77
Other Income (Loss) [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Lower of amortized cost or fair value adjustment	(16)	0	(25)	0
Residential mortgage banking revenue (expense) [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue associated with the economic hedging program (less than)	$ 0	$ 1	$ (1)	$ (1)