Allowance for Credit Losses - Accrued Interest Receivables (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Total accrued interest receivables	$ 321
Allowance for credit losses	3
Accrued interest receivables, net	318
Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Total accrued interest receivables	177
Accrued interest receivables charged off during the period	1
Securities Held-to-maturity [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Total accrued interest receivables	32
Other Financial Assets Measured at Amortized Cost [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Total accrued interest receivables	3
Securities available-for-sale [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Total accrued interest receivables	$ 109