Shareholders' Equity - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018
Class of Stock [Line Items]
Preferred Stock, Value, Issued	$ 1,700	$ 1,700
Dividend Rate	4.80%
Proceeds from Issuance of Preferred Stock and Preference Stock	$ 1,700	1,683	$ 0
Preferred Stock, Shares Issued	68,000
Preferred Stock, Value, Redeemed	$ (1,725)	$ (1,725)
Difference in redemption price and carrying value	$ 46
Series D
Class of Stock [Line Items]
Stock Redeemed or Called During Period, Shares	23,000
Series E
Class of Stock [Line Items]
Stock Redeemed or Called During Period, Shares	46,000
Redeemable preferred stock
Class of Stock [Line Items]
Preferred Stock, Value, Redeemed	$ 1,700