Income Taxes (Narrative) (Details) $ / shares in Units, $ in Millions, kr in Billions		6 Months Ended	12 Months Ended
	Dec. 31, 2017 USD ($)	Mar. 29, 2019 USD ($)	Dec. 31, 2020 USD ($) $ / shares	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($)	Dec. 31, 2019 DKK (kr)	Dec. 10, 2013 DKK (kr)
Net deferred tax liabilities			$ (3,454)	$ (1,652)
Valuation allowance, deferred tax asset, change in amount			3
Basis differences in investments outside the U.S.			$ 10,300
Statutory federal income tax rate	21.00%		21.00%	21.00%	21.00%	35.00%
Effective income tax rate			18.90%	26.40%	18.80%
Effective income tax rate reconciliation, other reconciling items, percent			0.70%	6.50%	1.20%
Income tax payments			$ 1,100	$ 847	$ 673
Employee service share-based compensation, tax benefit from exercise of stock options			110	79	57
Excess tax benefit from share-based compensation, operating activities			85	55	38
Income taxes receivable			700	196
Net operating loss carryforwards			452
Operating loss carryforwards, valuation allowances			174
Deferred tax assets, valuation allowances			264	261
Gross unrecognized tax benefits	$ 737		1,175	1,181	986	$ 737
Unrecognized tax benefits, net of offsetting indirect tax benefits			1,400	1,400
Unrecognized tax benefits, indirect tax benefits			148	131
Potential interest and penalties			(354)	(320)
Recognized potential interest and penalties			41	227	41
Unrecognized tax benefits that would impact effective tax rate			1,400	1,300
Estimated reduction in unrecognized tax benefits within twelve months			(199)
General business and foreign tax credit
Tax credit carryforwards			117
Tax credit carryforward, valuation allowance			66
Deferred tax asset, other
Deferred tax assets, valuation allowances			24
Domestic tax authority | IRS
Proposed adjustments to taxable income, self-insurance, other		$ 2,700
Foreign tax authority
Income tax examination, amount of tax assessments 2004-2009			309					kr 1.9
Income tax examination, amount of tax assessments 2010-2015			302				kr 1.8
Income tax holiday, aggregate dollar amount			$ 43	$ 71	$ 69
Income tax holiday, income tax benefits per diluted common share | $ / shares			$ 0.06	$ 0.10	$ 0.10
United States
Net deferred tax liabilities			$ (1,900)	$ (1,600)
International
Net deferred tax liabilities			$ (1,600)	$ (90)