Income Taxes - Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Loss carryforwards U.S. - Federal/States	$ 245	$ 188
Loss carryforwards - Foreign	3,876	3,232
Accrued liabilities, reserves, and other expenses	2,457	1,373
Stock-based compensation	2,033	1,585
Depreciation and amortization	1,886	2,385
Operating lease liabilities	10,183	6,648
Other items	559	728
Tax credits	207	772
Total gross deferred tax assets	21,446	16,911
Less valuation allowance	(5,803)	(5,754)
Deferred tax assets, net of valuation allowances	15,643	11,157
Deferred tax liabilities:
Depreciation and amortization	(5,508)	(5,507)
Operating lease assets	(9,539)	(6,331)
Other items	(1,462)	(640)
Net deferred tax assets (liabilities), net of valuation allowances	$ (866)	$ (1,321)