Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits	$ 3.5			$ 3.3
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%	35.00%
State income taxes, net of federal benefit	4.50%	3.30%
Tax benefits from stock compensation	(1.50%)	(1.30%)
Tax credits	(1.10%)	(0.40%)
Other	1.50%	(0.30%)
Walter Energy accrual	(0.30%)	(5.80%)