Derivatives - Interest Rate Swaps (Details) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2024		Jun. 30, 2023		Jun. 30, 2024		Jun. 30, 2023		Dec. 31, 2023
Derivatives
Tax expense		$ (0.2)		$ (1.8)		$ (1.1)		$ (1.4)
Unrealized gain on designated cash flow hedge	[1]	0.1	[2]	5.7	[3]	3.1	[4]	4.5	[5]
Fair value of derivative assets—current		62.5				62.5				$ 76.9
Fair value of derivative assets—long-term		11.3				11.3				27.0
Fair value of derivative liabilities—current		(64.1)				(64.1)				(62.7)
Fair value of derivative liabilities—long-term		(13.1)				(13.1)				(26.7)
Interest income		1.5		1.1		3.0		1.6
Interest rate swap
Derivatives
Change in fair value of interest rate swap		0.3		7.5		4.2		5.9
Tax expense		(0.2)		(1.8)		(1.1)		(1.4)
Unrealized gain on designated cash flow hedge		0.1		$ 5.7		3.1		$ 4.5
Fair value of derivative assets—current		4.4				4.4				3.3
Fair value of derivative assets—long-term		0.7				0.7				0.0
Fair value of derivative liabilities—long-term		0.0				0.0				(2.4)
Net fair value of commodity derivatives		5.1				5.1				0.9
Commodity swaps
Derivatives
Fair value of derivative assets—current		58.1				58.1				73.6
Fair value of derivative assets—long-term		10.6				10.6				27.0
Fair value of derivative liabilities—current		(64.1)				(64.1)				(62.7)
Fair value of derivative liabilities—long-term		(13.1)				(13.1)				(24.3)
Net fair value of commodity derivatives		$ (8.5)				$ (8.5)				$ 13.6

[1] Includes tax expense of $0.2 million and $1.1 million for the three and six months ended June 30, 2024, respectively, and tax expense of $1.8 million and $1.4 million for the three and six months ended June 30, 2023, respectively.

[2] Includes tax expense of $0.2 million for the three months ended June 30, 2024.

[3] Includes tax expense of $1.8 million for the three months ended June 30, 2023.

[4] Includes tax expense of $1.1 million for the six months ended June 30, 2024.

[5] Includes tax expense of $1.4 million for the six months ended June 30, 2023.