Fair Value Measurements Fair Value, Assets Measured on Nonrecurring Basis Using Unobservable Inputs (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring fair value losses	$ (63)	$ (75)
Fair Value Measurements Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring fair value losses	(63)	(64)
Fair Value Measurements Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	45	112
Operating Lease Equipment And Assets Held For Sale Or Re-Lease [Member] | Fair Value Measurements Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring fair value losses	(16)	(31)
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 Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	45	89
Property, Plant and Equipment [Member] | Fair Value Measurements Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring fair value losses		(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 Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure		8
Investments [Member] | Fair Value Measurements Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring fair value losses	(47)	(30)
Investments [Member] | Fair Value Measurements Nonrecurring [Member] | Level 3 [Member] | Valuation, Income Approach [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure		1
Other assets and Acquired intangible assets [Member] | Fair Value Measurements Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring fair value losses		(1)
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 Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure		$ 14