Loans Held for Sale - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	$ 512	$ 715
Revenue associated with the economic hedging program	(1,131)	1,136	$ 414
Transfer of loans to held for sale, net	1,042	1,253	1,588
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	394	648
Valuation allowance	3	10
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	118	67
Valuation allowance	4	5
Commercial Loans - Fair Value Option [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	109	471
Commercial Loans - Transferred to Held for Sale [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	285	62
Commercial Real Estate [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	27	115
Residential Mortgage [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	65	6
Lower of amortized cost or fair value adjustment attributed to non-credit factors			45
Loans held for sale, sold, unpaid principal balance		364
Loans held for sale, sold, at aggregate carrying value		276
Gain (loss) on sale of loans held for sale		(2)
Transfer of loans to held-for-sale, unpaid principal balance			568
Transfer of loans to held for sale, net			473
Residential Mortgage And Home Equity [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for sale, sold, unpaid principal balance		581
Loans held for sale, sold, at aggregate carrying value		536
Gain (loss) on sale of loans held for sale		50
Lower of cost or fair value adjustment attributed to credit factors		(1)
Transfer of loans to held-for-sale, unpaid principal balance			648
Transfer of loans to held for sale, net			628
Other Income (Loss) [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Lower of amortized cost or fair value adjustment attributed to non-credit factors	(5)	(5)	35
Other Income (Loss) [Member] | Residential Mortgage [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Additional lower of amortized cost or fair value adjustment		$ (5)	8
Other Income (Loss) [Member] | Residential Mortgage And Home Equity [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Additional lower of amortized cost or fair value adjustment			4
Residential mortgage banking revenue (expense) [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue associated with the economic hedging program	$ (1)
Provision for Credit Losses [Member] | Residential Mortgage And Home Equity [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Lower of cost or fair value adjustment attributed to credit factors			$ 11