Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions			3 Months Ended
	Oct. 06, 2017	Apr. 19, 2016	Dec. 31, 2018	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
Settlement Agreements
Loss Contingencies [Line Items]
Settlement agreement, amount claimants agreed to pay			$ 16.4
Indebtedness Claims | Notes holders
Loss Contingencies [Line Items]
Claim reserve account after emergence from bankruptcy					$ 400.0
Claim reserve account after effective date	$ 400.0
Royalties | ONRR
Loss Contingencies [Line Items]
Bankruptcy claims amount		$ 35.1