Shareholders' Equity - Summary of Preferred Stock (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Liquidation Amount	$ 5,141
Preferred Stock, Including Additional Paid in Capital, Net of Discount	5,102	$ 3,053
Series F
Class of Stock [Line Items]
Liquidation Amount	450
Preferred Stock, Including Additional Paid in Capital, Net of Discount	$ 437
Dividend Rate	5.20%
Series G
Class of Stock [Line Items]
Liquidation Amount	$ 500
Preferred Stock, Including Additional Paid in Capital, Net of Discount	$ 487
Dividend Rate	5.20%
Series H
Class of Stock [Line Items]
Liquidation Amount	$ 465
Preferred Stock, Including Additional Paid in Capital, Net of Discount	$ 450
Dividend Rate	5.625%
Series I
Class of Stock [Line Items]
Liquidation Amount	$ 173
Preferred Stock, Including Additional Paid in Capital, Net of Discount	$ 168
Dividend Rate	4.00%
Series J
Class of Stock [Line Items]
Liquidation Amount	$ 103
Preferred Stock, Including Additional Paid in Capital, Net of Discount	$ 92
Dividend Rate	4.00%
Series K
Class of Stock [Line Items]
Liquidation Amount	$ 500
Preferred Stock, Including Additional Paid in Capital, Net of Discount	$ 503
Dividend Rate	5.754%
Series L
Class of Stock [Line Items]
Liquidation Amount	$ 750
Preferred Stock, Including Additional Paid in Capital, Net of Discount	$ 766
Dividend Rate	5.05%
Series M
Class of Stock [Line Items]
Liquidation Amount	$ 500
Preferred Stock, Including Additional Paid in Capital, Net of Discount	$ 516
Dividend Rate	5.125%
Series N
Class of Stock [Line Items]
Liquidation Amount	$ 1,700
Preferred Stock, Including Additional Paid in Capital, Net of Discount	$ 1,683
Dividend Rate	4.80%