Shareholders' Equity (Preferred Stock) (Details) - USD ($) shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Common Stock Held in Trust	$ 13	$ 13
Preferred stock, authorized shares	4,400	4,400
Carrying value, Preferred stock	$ 566	$ 566
Parent [Member] | Series A Preferred Stock [Member]
Schedule of Equity Method Investments [Line Items]
Rate	> of 4.0% or 3mL+0.52%
Earliest redemption date	Dec. 15, 2011
Preferred stock, authorized shares	140,000
Outstanding Shares at December 31, 2012	66,139
Carrying value, Preferred stock	$ 67	67
Parent [Member] | Series G Preferred Stock [Member]
Schedule of Equity Method Investments [Line Items]
Earliest redemption date	Mar. 15, 2023
Preferred stock, authorized shares	200,000
Outstanding Shares at December 31, 2012	138,391
Carrying value, Preferred stock	$ 138	138
Preferred Stock, Dividend Rate, Percentage	6.30%
Parent [Member] | Series H Preferred Stock [Member]
Schedule of Equity Method Investments [Line Items]
Earliest redemption date	Jun. 15, 2019
Preferred stock, authorized shares	126,221
Outstanding Shares at December 31, 2012	126,221
Carrying value, Preferred stock	$ 126	126
Preferred Stock, Dividend Rate, Percentage	5.75%
Parent [Member] | Series I Preferred Stock [Member]
Schedule of Equity Method Investments [Line Items]
Earliest redemption date	Jun. 15, 2023
Preferred stock, authorized shares	300,893
Outstanding Shares at December 31, 2012	98,555
Carrying value, Preferred stock	$ 99	99
Preferred Stock, Dividend Rate, Percentage	5.80%
Parent [Member] | Series J Preferred Stock [Member]
Schedule of Equity Method Investments [Line Items]
Earliest redemption date	Sep. 15, 2023
Preferred stock, authorized shares	195,152
Outstanding Shares at December 31, 2012	136,368
Carrying value, Preferred stock	$ 136	$ 136
Preferred Stock, Dividend Rate, Percentage	7.20%