Fair Value Measurements Fair Value, Assets Measured on Nonrecurring Basis Using Unobservable Inputs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Sep. 30, 2016
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Nonrecurring fair value losses	$ (113)	$ (90)	$ (167)
Fair Value Measurements Nonrecurring [Member] | Investments [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Nonrecurring fair value losses	(44)
Fair Value Measurements Nonrecurring [Member] | Operating Lease Equipment [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Nonrecurring fair value losses	(32)	(52)
Fair Value Measurements Nonrecurring [Member] | Property, Plant and Equipment [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Nonrecurring fair value losses	(2)	(9)
Fair Value Measurements Nonrecurring [Member] | Other assets and Acquired intangible assets [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Nonrecurring fair value losses	(23)	(10)
Fair Value Measurements Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Total Fair Value	113	106
Nonrecurring fair value losses	(101)	(71)
Fair Value Measurements Nonrecurring [Member] | Level 3 [Member] | Market Approach Valuation Technique [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Operating Lease Equipment, Fair Value	90	84
Fair Value Measurements Nonrecurring [Member] | Level 3 [Member] | Income Approach Valuation Technique [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	1
Property, Plant, and Equipment, Fair Value	8	10
Other assets and Acquired intangible assets, Fair Value	$ 14	$ 12