Debt - Narrative (Details)	3 Months Ended			6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2022	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2022	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Jun. 30, 2022	Mar. 16, 2022 USD ($)	Jun. 30, 2021 USD ($)	Mar. 26, 2021 USD ($)	Jul. 10, 2020 USD ($)
Debt Instrument [Line Items]
Long-term debt		$ 990,900,000			$ 990,900,000				$ 694,500,000
Letters of credit issued		5,800,000			5,800,000
Interest costs		11,400,000	$ 10,100,000		32,000,000	$ 30,400,000
Interest costs, capitalized		200,000	1,200,000		500,000	6,900,000
Debt prepayment costs		0	0		$ 0	(8,200,000)
Fair value hedging
Debt Instrument [Line Items]
Derivative, gain on derivative						2,300,000
Fair value hedging | Interest Rate Swaps
Debt Instrument [Line Items]
Derivative, gain on derivative						2,300,000
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		0			$ 0
Credit Agreement available for future borrowings		$ 294,200,000			$ 294,200,000
Borrowing rate		2.45%			2.45%
Minimum available liquidity		$ 150,000,000			$ 150,000,000
Asset coverage ratio					1.10
Revolving Credit Facility | Line of Credit | Forecast
Debt Instrument [Line Items]
Required interest coverage ratio one							2.00
Required interest coverage ratio two	3.00			3.50
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%
Required debt to capital ratio (less than)		0.55			0.55
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%	7.625%
Long-term debt		$ 295,600,000			$ 295,600,000				$ 0
Senior unsecured notes, 4.45% due March 2023
Debt Instrument [Line Items]
Face amount		$ 300,000,000			$ 300,000,000				$ 300,000,000
Interest rate		4.45%			4.45%				4.45%	4.45%
Long-term debt		$ 299,700,000			$ 299,700,000				$ 299,500,000	$ 300,000,000
Senior unsecured notes, 6.375% due July 2028
Debt Instrument [Line Items]
Face amount		$ 400,000,000			$ 400,000,000				$ 400,000,000		$ 400,000,000
Interest rate		6.375%			6.375%				6.375%		6.375%
Long-term debt		$ 395,600,000			$ 395,600,000				$ 395,000,000.0
Senior unsecured notes, 5.20% due July 2021
Debt Instrument [Line Items]
Face amount											$ 250,000,000
Debt prepayment costs		$ 0	$ 0		$ 0	$ 10,500,000