Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions				1 Months Ended	3 Months Ended	6 Months Ended
	Aug. 31, 2019	Oct. 06, 2017	Apr. 19, 2016	Jul. 31, 2019	Dec. 31, 2018	Jun. 30, 2019	Aug. 08, 2019	Mar. 31, 2019	Apr. 14, 2017
Loss Contingencies [Line Items]
Claims settled		$ 399.0
Bankruptcy claims, undistributed amount returned		1.3
Bankruptcy claims amount of claims settled, make-whole fees		223.8
Bankruptcy claims amount of claims settled, postpetition interest		$ 175.2
Claims subject to Appellate Court decision						$ 260.0		$ 260.0
Payments for legal settlement						3.5
Royality Interest dispute expense						$ 1.5
Subsequent Event
Loss Contingencies [Line Items]
Claims subject to Appellate Court decision							$ 240.0
Settlement Agreements
Loss Contingencies [Line Items]
Settlement agreement, amount claimants agreed to pay					$ 16.4
Settlement Agreements | Subsequent Event
Loss Contingencies [Line Items]
Settlement agreement, amount claimants agreed to pay				$ 13.5
ONRR | Subsequent Event
Loss Contingencies [Line Items]
Settlement agreement, amount claimants agreed to pay	$ 12.4
Period for payment of installments	60 months
Indebtedness Claims | Notes holders
Loss Contingencies [Line Items]
Claim reserve account after emergence from bankruptcy									$ 400.0
Royalties | ONRR
Loss Contingencies [Line Items]
Bankruptcy claims amount			$ 35.1