Securities - Amounts Recognized in Income from Available-for-Sale and Trading Securities (Parenthetical) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Equity securities unrealized gains (losses)	$ (6)	$ 23	$ (12)