Income Taxes (Components of Net Deferred Tax Liability) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred Tax Assets:
Net operating loss and other loss carryforwards	$ 2,017	$ 1,926
Nondeductible accruals and other	2,779	2,656
Less: Valuation allowance	1,906	632
Total deferred tax assets, net of valuation allowance	2,890	3,950
Deferred Tax Liabilities:
Differences between book and tax basis of property and equipment and intangible assets	29,387	29,139
Differences between book and tax basis of investments	702	491
Differences between book and tax basis of long-term debt	751	604
Differences between book and tax basis of foreign subsidiaries and undistributed foreign earnings	143	85
Total deferred tax liabilities	30,983	30,319
Net deferred tax liability	$ 28,093	$ 26,369