Investment Securities (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) Securities	Dec. 31, 2017 USD ($) Securities	Dec. 31, 2016 USD ($)
Investment [Line Items]
Interest on securities	$ 350	$ 326	$ 204
Number of HTM investment securities in an unrealized loss position | Securities	606	667
Number of AFS investment securities in an unrealized loss position | Securities	2,588	2,262
Carrying value of pledged securities	$ 2,600	$ 2,100
Available-for-sale Securities, Amortized Cost Basis	15,040	$ 15,313
Private equity investments prohibited by Volker rule	3
Commitments for Private Equity and Other Noninterest-bearing Investments	30
Private Equity Investments	147
Commitments for Private Equity or Other Non-Interest Bearing Investments Prohibited by the Volcker Rule	$ 2