Income Tax (Interest Accrued Related to Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Examination [Line Items]
Interest expense (benefit) recognized on the consolidated statements of operations (1)	$ 12	$ (179)	$ (441)
Interest included in other liabilities on the consolidated balance sheets	51	39
Operating Expense
Income Tax Examination [Line Items]
Interest expense (benefit) recognized on the consolidated statements of operations (1)	60	168
Current Income Tax Payable
Income Tax Examination [Line Items]
Interest expense (benefit) recognized on the consolidated statements of operations (1)	$ 119	$ 273