Commitments - Narrative (Details) $ in Millions	Sep. 30, 2017 USD ($)
Drilling Rig Leases [Member]
Long-term Purchase Commitment [Line Items]
Contractual Obligation	$ 31

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration