Fair Value Measurements Fair Value, Assets Measured on Nonrecurring Basis Using Unobservable Inputs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Nonrecurring fair value losses	$ (93)	$ (113)	$ (90)
Fair Value Measurements Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Nonrecurring fair value losses	(93)	(101)
Assets, Fair Value Disclosure	145	113
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	(4)	(2)
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	44	8
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		(23)
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		14
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	(39)	(32)
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	101	90
Investments [Member] | Fair Value Measurements Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Nonrecurring fair value losses	(50)	(44)
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		$ 1