Marketable Securities (Tables)

3 Months Ended

Dec. 31, 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 gains (losses) on the short-term and long-term marketable securities as of December 31, 2022 and September 30, 2022 (in thousands):

			Gross		Gross
	Amortized		Unrealized		Unrealized
	Cost		Losses		Gains		Fair Value
December 31, 2022:
U.S. Treasury securities and obligations of U.S. government agencies	$	479,617	$	(5,434)	$	13	$	474,196
Bank certificates of deposits		10,549		(174)		5		10,380
Corporate securities		341,317		(6,941)		—		334,376
Municipal securities		8,633		(13)		—		8,620
	$	840,116	$	(12,562)	$	18	$	827,572
September 30, 2022:
U.S. Treasury securities and obligations of U.S. government agencies	$	804,774	$	(6,163)	$	21	$	798,632
Bank certificates of deposits		8,335		(158)	$	1	$	8,178
Corporate securities		406,270		(8,113)		—		398,157
Municipal securities		59,043		(226)		—		58,817
	$	1,278,422	$	(14,660)	$	22	$	1,263,784

Fair Value of Marketable Securities by Contractual Maturity

The fair values of the marketable securities by contractual maturities at December 31, 2022 are presented below (in thousands):

	Amortized
	Cost			Fair Value
Due in one year or less	$	525,787	$	522,897
Due after one year through five years		311,387		301,734
Due after five years through ten years		—		—
Due after ten years		2,942		2,941
Total marketable securities	$	840,116	$	827,572