Fair Value, Assets Measured On Nonrecurring Basis, Valuation Techniques (Details) - USD ($) $ in Millions		Sep. 30, 2018	Sep. 30, 2017
Aircraft Value Publications [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair value of assets and liabilities measured on nonrecurring basis valuation techniques, median		$ 46
Aircraft Value Publications [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range of fair value of assets measured on nonrecurring basis valuation techniques	[1]	41
Aircraft Value Publications [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range of fair value of assets measured on nonrecurring basis valuation techniques	[1]	63
Aircraft Condition Adjustments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Net fair value of assets measured on nonrecurring basis valuation techniques		(1)
Aircraft Condition Adjustments [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range of fair value of assets measured on nonrecurring basis valuation techniques	[2]	(4)
Aircraft Condition Adjustments [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range of fair value of assets measured on nonrecurring basis valuation techniques	[2]	3
Fair Value Measurements Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [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] | Level 3 [Member] | Valuation, Market Approach [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure		$ 45	$ 89

[1] The range represents the sum of the highest and lowest values for all aircraft subject to fair value measurement, according to the third party aircraft valuation publications that we use in our valuation process.

[2] The negative amount represents the sum for all aircraft subject to fair value measurement, of all downward adjustments based on consideration of individual aircraft attributes and condition. The positive amount represents the sum of all such upward adjustments.