Income Taxes (Narrative) (Details) kr in Millions, $ in Millions			3 Months Ended	12 Months Ended			36 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2012 DKK (kr)	Dec. 31, 2015 USD ($)	Dec. 10, 2013 DKK (kr)
Net deferred tax liabilities	$ 2,311.2	$ 2,333.3	$ 2,311.2	$ 2,311.2	$ 2,333.3
Valuation allowance, deferred tax asset, change in amount				65.0
Basis differences in investments outside the U.S.	9,500.0		9,500.0	$ 9,500.0
Statutory federal income tax rate		21.00%		21.00%	35.00%	35.00%
TCJA, effect on income tax expense, transition tax				$ 40.0	$ 1,200.0
TCJA, effect on income tax expense, transition tax payable, term				7 years	8 years
TCJA, effect on income tax expense, transition tax payable, amount	180.0		180.0	$ 180.0
TCJA, effect on income tax expense, transition tax, provision of unrealizable credits				13.0
TCJA, effect on income tax expense, remeasured deferred tax assets and liabilities				$ 47.0	$ 1,200.0
Effective income tax rate				19.50%	16.00%	17.50%
Effective income tax rate reconciliation, other reconciling items, percent				(0.70%)	(5.00%)	(3.50%)
Income tax payments				$ 673.0	$ 689.0	$ 767.0
Employee service share-based compensation, tax benefit from exercise of stock options				57.0	85.0	99.0
Excess tax benefit from share-based compensation, operating activities				38.0	55.0
Adjustments to additional paid in capital, income tax benefit from share-based compensation						50.0
Excess tax benefit from share-based compensation, financing activities						50.0
Net operating loss carryforwards	653.0		653.0	653.0
Operating loss carryforwards, valuation allowances	252.0		252.0	252.0
Deferred tax assets, valuation allowances	389.6	$ 324.6	389.6	389.6	324.6
Gross unrecognized tax benefits	986.0	736.8	986.0	986.0	736.8	992.2		$ 990.2
Recognized potential interest and penalties				41.0	41.0	47.0
Unrecognized tax benefits that would impact effective tax rate	936.0		936.0	936.0
Entity | United States
Net deferred tax liabilities	2,000.0	2,000.0	2,000.0	2,000.0	2,000.0
Entity | International
Net deferred tax liabilities	277.0	301.0	277.0	277.0	301.0
Foreign tax authority
Income tax examination, amount of tax assessments	247.0		247.0	247.0					kr 1,600
Income tax examination, amount of potential additional tax assessments	146.0						kr 954
Income tax holiday, aggregate dollar amount				70.0	62.0	$ 61.0
Deferred tax asset, other
Deferred tax assets, valuation allowances	49.0		49.0	49.0
Continuing operations
Gross unrecognized tax benefits	986.0	737.0	986.0	986.0	737.0
Unrecognized tax benefits, net of offsetting indirect tax benefits	988.0	736.0	988.0	988.0	736.0
Unrecognized tax benefits, indirect tax benefits	117.0	104.0	117.0	117.0	104.0
Potential interest and penalties	(119.0)	$ (103.0)	(119.0)	(119.0)	$ (103.0)
Estimated reduction in unrecognized tax benefits within twelve months	(134.0)		(134.0)	(134.0)
Continuing operations | General business and foreign tax credit
Tax credit carryforwards	241.0		241.0	241.0
Tax credit carryforward, valuation allowance	89.0		89.0	$ 89.0
IRS | Domestic tax authority
Proposed adjustments to taxable income, self-insurance			$ 960.0
Proposed adjustments to taxable income, self-insurance, other	$ 1,700.0