Condensed Financial Information (Parent Company) (Interest Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest Expense [Abstract]
Total interest expense	$ 656	$ 827	$ 841
Parent Company
Interest Expense [Abstract]
Total interest expense	850	1,009	1,108
Parent Company | Long-term Debt
Interest Expense [Abstract]
Total interest expense	591	755	774
Parent Company | Long-term Debt | Affiliated Entity [Member]
Interest Expense [Abstract]
Total interest expense	48	45	112
Parent Company | Secured Debt [Member]
Interest Expense [Abstract]
Total interest expense	6	6	27
Parent Company | Junior Subordinated Debt [Member]
Interest Expense [Abstract]
Total interest expense	$ 205	$ 203	$ 195