Income Taxes (Unrecognized Tax Benefit Changes) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2020
Significant Change In Unrecognized Tax Benefits Is Reasonably Possible [Line Items]
Effective Income Tax Rate Reconciliation, Percent	1.00%	0.50%	(22.00%)	7.40%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	22.50%		12.70%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Impairment Losses, Percent	17.40%		24.60%
Effective income tax rate reconciliation, debt exchange, percent	1.60%		2.20%
Effective Income Tax Rate Reconciliation, Tax Credit, Foreign, Percent	1.20%		1.70%
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent	1.80%		0.70%
Effective Income Tax Rate Reconciliation, Deferred Tax Assets, Percent			14.30%
Unrecognized Tax Benefits, Period Increase (Decrease)	$ (440)
Unrecognized Tax Benefits, Increase Resulting from Acquisition	240
Unrecognized Tax Benefits, Interest on Income Taxes Expense	11		$ 13
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	126		126
Minimum [Member]
Significant Change In Unrecognized Tax Benefits Is Reasonably Possible [Line Items]
Decrease in Unrecognized Tax Benefits is Reasonably Possible, Estimated Range of Change	140		140
Minimum [Member] | Forecast [Member]
Significant Change In Unrecognized Tax Benefits Is Reasonably Possible [Line Items]
Effective Income Tax Rate Reconciliation, Tax Settlement, Amount					$ 75
Maximum [Member]
Significant Change In Unrecognized Tax Benefits Is Reasonably Possible [Line Items]
Decrease in Unrecognized Tax Benefits is Reasonably Possible, Estimated Range of Change	$ 275		$ 275
Maximum [Member] | Forecast [Member]
Significant Change In Unrecognized Tax Benefits Is Reasonably Possible [Line Items]
Effective Income Tax Rate Reconciliation, Tax Settlement, Amount					$ 125