Parent Company (Interest Paid and Income Tax Refunds (Payments)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Financial Statements, Captions [Line Items]
Interest paid	$ 1,292	$ 3,742	$ 2,835
Income Tax Refunds/(Payments)	10	17	468
Parent Company
Condensed Financial Statements, Captions [Line Items]
Interest paid	335	300	288
Income Tax Refunds/(Payments)	$ 29	$ 26	$ 88