Shareholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Class of Stock [Line Items]
Preferred stock par value (in dollars per share)	$ 0.01		$ 0.01
Fixed-to-Floating Rate Cumulative Preferred Stock Series A [Member]
Class of Stock [Line Items]
Preferred stock dividends paid	$ 29	$ 30
Preferred stock shares issued	1,000,000		1,000,000
Fixed-to-Floating Rate Cumulative Perpetual Preferred Stock, Series B [Member]
Class of Stock [Line Items]
Preferred stock dividends paid	$ 17
Preferred stock shares issued	500,000		500,000