Income Tax (Interest Accrued Related to Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Examination [Line Items]
Interest expense (benefit) recognized on the consolidated statements of operations (1)	$ (441)	$ 37	$ (41)
Interest included in other liabilities on the consolidated balance sheets	218	$ 659
Operating Expense
Income Tax Examination [Line Items]
Interest expense (benefit) recognized on the consolidated statements of operations (1)	168
Current Income Tax Payable
Income Tax Examination [Line Items]
Interest expense (benefit) recognized on the consolidated statements of operations (1)	$ 273