Debt - Narrative (Details)	3 Months Ended		6 Months Ended
	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2022 USD ($) Rate	Dec. 31, 2021 USD ($)	Dec. 31, 2022	Dec. 31, 2022 Rate	Sep. 30, 2022	Sep. 30, 2022 Rate	Jun. 30, 2022 USD ($)	Jun. 30, 2022	Jun. 30, 2022 Rate	Apr. 30, 2022 USD ($)	Mar. 16, 2022 USD ($)	Mar. 26, 2021 USD ($)
Debt Instrument [Line Items]
Long-term debt	$ 692,400,000		$ 692,400,000						$ 691,800,000
Letters of credit issued	1,800,000		1,800,000
Short-term credit agreement borrowings	81,200,000		81,200,000						0
Interest costs	13,300,000	$ 10,300,000	26,100,000	$ 20,600,000
Interest costs, capitalized	300,000	$ 200,000	$ 500,000	$ 300,000
Line of Credit | Maximum
Debt Instrument [Line Items]
Required debt to capital ratio (less than)										0.55
Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Current borrowing capacity														$ 300,000,000
Debt instrument, covenant, credit commitment amount														300,000,000
Maximum borrowing capacity														500,000,000
Commitment fee rate			0.35%
Short-term credit agreement borrowings	81,200,000		$ 81,200,000
Credit Agreement available for future borrowings	217,000,000		$ 217,000,000
Borrowing rate					6.38%
Required interest coverage ratio one										2.00	200.00%
Required interest coverage ratio two					3.50	350.00%	3.00	300.00%
Asset coverage ratio | Rate			110.00%
Revolving Credit Facility | Line of Credit | LIBOR
Debt Instrument [Line Items]
Interest rate margin			2.00%
Revolving Credit Facility | Line of Credit | Base Rate
Debt Instrument [Line Items]
Interest rate margin			1.00%
Revolving Credit Facility | Line of Credit | Minimum
Debt Instrument [Line Items]
Commitment fee rate			0.275%
Revolving Credit Facility | Line of Credit | Minimum | LIBOR
Debt Instrument [Line Items]
Interest rate margin			1.25%
Revolving Credit Facility | Line of Credit | Minimum | Base Rate
Debt Instrument [Line Items]
Interest rate margin			0.25%
Revolving Credit Facility | Line of Credit | Maximum
Debt Instrument [Line Items]
Commitment fee rate			0.375%
Revolving Credit Facility | Line of Credit | Maximum | LIBOR
Debt Instrument [Line Items]
Interest rate margin			2.25%
Revolving Credit Facility | Line of Credit | Maximum | Base Rate
Debt Instrument [Line Items]
Interest rate margin			1.25%
Letters of credit | Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity														$ 40,000,000
Letter of credit fees			2.00%
Letters of credit | Line of Credit | Minimum
Debt Instrument [Line Items]
Letter of credit fees			1.25%
Letters of credit | Line of Credit | Maximum
Debt Instrument [Line Items]
Letter of credit fees			2.25%
Senior unsecured notes, 7.625% due March 2030
Debt Instrument [Line Items]
Face amount	300,000,000		$ 300,000,000						300,000,000				$ 300,000,000
Interest rate					7.625%					7.625%			7.625%
Long-term debt	$ 296,200,000		$ 296,200,000						$ 295,900,000
Senior unsecured notes, 4.45% due March 2023
Debt Instrument [Line Items]
Face amount												$ 300,000,000
Interest rate												4.45%		4.45%
Long-term debt														$ 300,000,000