Subsequent Events (Details) - Subsequent Event [Member] $ in Millions	3 Months Ended
Dec. 31, 2018 USD ($)
Subsequent Event [Line Items]
Proceeds from formation of new mineral relationship	$ 215
Combined per year acquisitions of additional mineral interests	$ 125

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration