Fair Value Measurements Fair Value, Assets Measured On Nonrecurring Basis, Valuation Techniques (Details) $ in Millions	Sep. 30, 2019 USD ($)
Aircraft Value Publications [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of assets and liabilities measured on nonrecurring basis valuation techniques, median	$ 16
Aircraft Value Publications [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of fair value of assets measured on nonrecurring basis valuation techniques	12
Aircraft Value Publications [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of fair value of assets measured on nonrecurring basis valuation techniques	20
Aircraft Condition Adjustments [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Net fair value of assets measured on nonrecurring basis valuation techniques	(6)
Aircraft Condition Adjustments [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of fair value of assets measured on nonrecurring basis valuation techniques	(6)
Aircraft Condition Adjustments [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range of fair value of assets measured on nonrecurring basis valuation techniques	$ 0