Fair Value Measurements Fair Value, Assets Measured on Nonrecurring Basis Using Unobservable Inputs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Nonrecurring fair value losses	$ (410)	$ (443)	$ (93)
Fair Value Measurements Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Nonrecurring fair value losses	(410)	(443)
Fair Value Measurements Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	504	183
Investments [Member] | Fair Value Measurements Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Nonrecurring fair value losses	(81)	(109)
Investments [Member] | Fair Value Measurements Nonrecurring [Member] | Level 3 [Member] | Valuation, Income Approach [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	22	27
Operating Lease Equipment And Assets Held For Sale Or Re-Lease [Member] | Fair Value Measurements Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Nonrecurring fair value losses	(24)	(20)
Operating Lease Equipment And Assets Held For Sale Or Re-Lease [Member] | Fair Value Measurements Nonrecurring [Member] | Level 3 [Member] | Valuation, Market Approach [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	105	111
Other assets and Acquired intangible assets [Member] | Fair Value Measurements Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Nonrecurring fair value losses	(221)	(310)
Other assets and Acquired intangible assets [Member] | Fair Value Measurements Nonrecurring [Member] | Level 3 [Member] | Valuation, Income Approach [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	298	4
Property, Plant and Equipment [Member] | Fair Value Measurements Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Nonrecurring fair value losses	(84)	(4)
Property, Plant and Equipment [Member] | Fair Value Measurements Nonrecurring [Member] | Level 3 [Member] | Valuation, Income Approach [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 79	$ 41