Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	Oct. 06, 2017	Aug. 31, 2016	Apr. 29, 2016	Apr. 19, 2016
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
Indebtedness Claims | Notes holders
Loss Contingencies [Line Items]
Claim reserve account after effective date	$ 400.0
Royalties | ONRR
Loss Contingencies [Line Items]
Bankruptcy claims amount				$ 35.1
Oil Sales Contract | SPMT
Loss Contingencies [Line Items]
Bankruptcy claims amount		$ 16.9
Damage sought			$ 38.6