Properties And Equipment - Summary of Acquisitions (Details) $ in Millions		3 Months Ended
		Dec. 31, 2021 USD ($) a	Dec. 31, 2020 USD ($) a
Haynesville /LA [Member]
Property Plant And Equipment [Line Items]
Net royalty acres | a	[1],[2]	426
Purchase Price | $	[2]	$ 5.8
Haynesville /LA [Member]
Property Plant And Equipment [Line Items]
Net royalty acres | a	[1],[2]	847
Purchase Price | $	[2]	$ 4.1
SCOOP / OK [Member]
Property Plant And Equipment [Line Items]
Net royalty acres | a	[1],[2]	172	297
Purchase Price | $	[2]	$ 1.4	$ 2.3
Haynesville / TX [Member]
Property Plant And Equipment [Line Items]
Net royalty acres | a	[1],[2]	103	142
Purchase Price | $	[2]	$ 0.6	$ 1.0
Haynesville /LA [Member]
Property Plant And Equipment [Line Items]
Net royalty acres | a	[1],[2]	116
Purchase Price | $	[2]	$ 1.7
SCOOP / OK [Member]
Property Plant And Equipment [Line Items]
Net royalty acres | a	[1],[2]	220
Purchase Price | $	[2]	$ 1.2
Haynesville / TX [Member]
Property Plant And Equipment [Line Items]
Net royalty acres | a	[1],[2]		184
Purchase Price | $	[2]		$ 0.8
Haynesville / TX [Member]
Property Plant And Equipment [Line Items]
Net royalty acres | a	[1],[2]		386
Purchase Price | $	[2]		$ 3.5

[1] An estimated net royalty equivalent was used for the minerals included in the net royalty acres.

[2] Excludes subsequent closing adjustments and insignificant acquisitions.