Derivatives - Interest Rate Swaps (Details) - USD ($)		3 Months Ended				6 Months Ended
		Jun. 30, 2020		Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Apr. 30, 2019
Derivatives
Derivative, notional amount									$ 850,000,000.0
Derivative, fixed interest rate									2.28%
Income tax (benefit)		$ 500,000	[1]	$ (4,000,000.0)	$ (3,600,000)	$ (3,500,000)	$ (3,600,000)
Gain (loss) on designated cash flow hedge	[1]	1,500,000		$ (13,100,000)	(9,900,000)	(11,600,000)	(9,900,000)
(Loss) gain on interest rate swaps		3,700,000			(300,000)	5,000,000.0	(300,000)
Interest expense expected to be reclassified out of accumulated other comprehensive income (loss) over the next twelve months		18,400,000				18,400,000
Fair value of derivative liabilities—current		(31,300,000)				(31,300,000)		$ (14,400,000)
Fair value of derivative liabilities—long-term		(9,400,000)				(9,400,000)		(6,800,000)
Interest rate swaps
Derivatives
Change in fair value of derivatives		2,000,000.0			$ (13,500,000)	(15,100,000)	$ (13,500,000)
Fair value of derivative liabilities—current		(18,300,000)				(18,300,000)		(5,600,000)
Fair value of derivative liabilities—long-term		(9,300,000)				(9,300,000)		(6,800,000)
Net fair value of commodity swaps		$ (27,600,000)				$ (27,600,000)		$ (12,400,000)

[1] Includes a tax expense of $0.5 million and a tax benefit of $3.5 million for the three and six months ended June 30, 2020, respectively, and a tax benefit of $3.6 million for the three and six months ended June 30, 2019, respectively.