Leases (Components of Operating Lease Costs) (Details) - USD ($) $ in Thousands		3 Months Ended	9 Months Ended
		Jun. 30, 2020	Jun. 30, 2020
Lessee, Lease, Description [Line Items]
Operating Lease Expense		$ 956	$ 2,872
Variable Lease Expense	[1]	108	380
Short-Term Lease Expense/Costs	[2]	46	186
Sublease Income		(41)	(202)
Total Lease Expense		1,069	3,236
Oil and Natural Gas Properties [Member]
Lessee, Lease, Description [Line Items]
Short-Term Lease Expense/Costs	[3]	$ 3,174	$ 17,463

[1] Variable lease payments that are not dependent on an index or rate are not included in the lease liability.

[2] Short-term lease costs exclude expenses related to leases with a lease term of one month or less.

[3] Short-term lease costs relating to drilling rig leases that are capitalized as part of oil and natural gas properties under full cost pool accounting.