Investments Available-for-Sale (Tables)

3 Months Ended

Dec. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Schedule of Amortized Cost and Fair Value of Available-for-Sale Securities

The following tables present the amortized cost and fair value of available-for-sale securities (dollars in millions):

December 31, 2019	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Available-for-sale securities:
U.S. Treasury securities	$	1,591	$	45	$	—	$	1,636

September 30, 2019	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Available-for-sale securities:
U.S. Treasury securities	$	1,591	$	77	$	—	$	1,668

Schedule of Contractual Maturities of Available-for-Sale Securities

The following table presents the contractual maturities of available-for-sale securities as of December 31, 2019 (dollars in millions):

	Amortized Cost		Fair Value
Available-for-sale U.S. Treasury securities:
Due within one to five years	$	582	$	612
Due within five to ten years	618		626
Due after ten years	391		398
Total available-for-sale U.S. Treasury securities	$	1,591	$	1,636