Borrowings - JPM Credit Facility (Narrative) (Details) - USD ($)	Jun. 07, 2024	Mar. 17, 2023	Sep. 13, 2022	Jun. 30, 2024	Sep. 30, 2023
Debt Instrument [Line Items]
Long-term debt				$ 4,315,465,000	$ 3,117,719,000
JPM Credit Facility | Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity				1,487,500,000
Amount of additional commitments	$ 512,500
Line of credit facility, commitment fee percentage		0.375%
Debt instrument, amortization period		1 year
Long-term debt				333,718,000	784,374,000
JPM Credit Facility | Revolving Credit Facility | Line of Credit | Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Line of credit facility, interest rate during period	0.10%
Debt instrument, basis spread on variable rate		0.10%
JPM Credit Facility | Revolving Credit Facility | Line of Credit | Secured Overnight Financing Rate (SOFR) | Minimum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate			0.11448%
JPM Credit Facility | Revolving Credit Facility | Line of Credit | Secured Overnight Financing Rate (SOFR) | Maximum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate			0.42826%
JPM Credit Facility | Revolving Credit Facility | Line of Credit | Base Rate | Minimum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	1.75%
JPM Credit Facility | Revolving Credit Facility | Line of Credit | Base Rate | Maximum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1.875%
JPM Credit Facility | Letter of Credit | Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 23,750,000
Long-term debt				$ 0	$ 0