Shareholders' Equity - Narrative (Details) - USD ($) shares in Thousands, $ in Millions	3 Months Ended			6 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Aug. 03, 2020	Jun. 19, 2020	Jun. 01, 2020	May 27, 2020
Class of Stock [Line Items]
Preferred Stock, Value, Issued		$ 2,600		$ 2,600
Preferred Stock, Value, Redeemed				503
Proceeds from Issuance of Preferred Stock and Preference Stock				$ 2,544	$ 0
Series K
Class of Stock [Line Items]
Stock Redeemed or Called During Period, Shares			5
Preferred Stock, Value, Redeemed			$ 500
Series O Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Value, Issued									$ 575
Dividend Rate		5.25%
Preferred Stock, Shares Issued		23
Proceeds from Issuance of Preferred Stock and Preference Stock		$ 559
Series P Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Value, Issued								$ 1,000
Dividend Rate		4.95%
Preferred Stock, Shares Issued		40
Proceeds from Issuance of Preferred Stock and Preference Stock		$ 992
Series Q Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Value, Issued							$ 1,000
Dividend Rate		5.10%
Preferred Stock, Shares Issued		40
Proceeds from Issuance of Preferred Stock and Preference Stock		$ 993
Series R Preferred Stock [Member] | Subsequent Event
Class of Stock [Line Items]
Preferred Stock, Value, Issued						$ 925
Dividend Rate	4.75%
Preferred Stock, Shares Issued	37
Proceeds from Issuance of Preferred Stock and Preference Stock	$ 908