Fair Value Measurements (Schedule Of Available For Sale Securities) (Details) - USD ($) $ in Millions |
Jun. 30, 2018 |
Sep. 30, 2017 |
---|---|---|
U.S. treasury and agency | ||
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
Amortized Cost Basis | $ 46 | $ 47 |
Fair Value | 45 | 47 |
Unrealized Gain (Loss) | (1) | 0 |
Corporate and asset-backed | ||
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
Amortized Cost Basis | 53 | 51 |
Fair Value | 53 | 51 |
Unrealized Gain (Loss) | $ 0 | $ 0 |