Marketable Securities (Tables)

9 Months Ended

Jun. 30, 2022

Investments, Debt and Equity Securities [Abstract]

Summary of Amortized Cost and Fair Value, Including Accrued Interest Receivable and Unrealized Holding Gains (Losses) on Short-term and Long-term Marketable Securities

The following is a summary of the amortized cost and the fair value, including accrued interest receivable as well as unrealized holding gains (losses) on the short-term and long-term marketable securities as of June 30, 2022 and September 30, 2021 (in thousands):

			Gross		Gross
	Amortized		Unrealized		Unrealized
	Cost		Losses		Gains		Fair Value
June 30, 2022:
U.S. Treasury securities and obligations of U.S. government agencies	$	536,322	$	(2,981)	$	93	$	533,434
Bank certificates of deposits		6,341		(45)		—		6,296
Corporate securities		372,922		(4,009)		159		369,072
Municipal securities		112,621		(334)		1		112,288
	$	1,028,206	$	(7,369)	$	253	$	1,021,090
September 30, 2021:
Bank certificates of deposits	$	30	$	—	$	—	$	30
Corporate securities		3,624		—		—		3,624
Municipal securities		—		—		—		—
Other debt securities		25		—		—		25
	$	3,679	$	—	$	—	$	3,679

Fair Value of Marketable Securities by Contractual Maturity

The fair values of the marketable securities by contractual maturities at June 30, 2022 are presented below (in thousands):

	Amortized
	Cost			Fair Value
Due in one year or less	$	711,599	$	708,895
Due after one year through five years		313,633		309,221
Due after five years through ten years		—		—
Due after ten years		2,974		2,974
Total marketable securities	$	1,028,206	$	1,021,090