Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits	$ 4.6		$ 4.5
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%
State income taxes, net of federal benefit	4.50%	4.50%
Tax benefits from stock compensation	(0.60%)	(1.50%)
Tax credits	(1.40%)	(1.10%)
Other	1.10%	1.50%
Walter Energy accrual	0.00%	(0.30%)