Shareholders' Equity - Narrative (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Fixed-to-Floating Rate Cumulative Preferred Stock Series A [Member]
Class of Stock [Line Items]
Preferred stock dividends paid	$ 29	$ 30
Fixed-to-Floating Rate Cumulative Perpetual Preferred Stock, Series B [Member]
Class of Stock [Line Items]
Preferred stock dividends paid	$ 17