Fair Value Option - Gains (Losses) Related to Borrower-specific Credit Risk (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Trading Securities
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) related to borrower-specific credit risk for assets accounted for under the fair value option	$ 13	$ 9
Loans and leases
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) related to borrower-specific credit risk for assets accounted for under the fair value option	19	(10)
Loans held-for-sale
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) related to borrower-specific credit risk for assets accounted for under the fair value option	$ 0	$ (1)