Income Taxes Income Taxes (Summary of Operating Loss and Tax Credit Carryforwards) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Operating Loss Carryforwards [Line Items]
Charitable Contributions	$ 2,097
Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss, subject to expiration	143,571
Net operating loss, not subject to expiration	54,789
Alternative Minimum Tax Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax Credit Carryforwards		$ 85,000
Alternative Minimum Tax Credit [Member] | Federal [Member]
Operating Loss Carryforwards [Line Items]
Tax Credit Carryforwards	42,546
Research and Development Tax Credit Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Tax Credit Carryforwards	6,339
Enhanced Oil Recovery Credit [Member] | Federal [Member]
Operating Loss Carryforwards [Line Items]
Tax Credit Carryforwards	26,790
Pennsylvania [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss	383,056
California [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss	207,995
California [Member] | Alternative Minimum Tax Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax Credit Carryforwards	7,711
California [Member] | Enhanced Oil Recovery Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax Credit Carryforwards	$ 8,504