Income Taxes Income Tax Rate Reconciliation (Details)	3 Months Ended		6 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%	35.00%
Adjustments to reconcile to the effective tax rate:
State income taxes, net of federal benefit	4.50%	3.30%
Valuation allowance adjustment related to stock compensation	(0.70%)	0.00%
Tax benefits from stock compensation	(1.50%)	(1.30%)
Tax credits	(1.10%)	(0.40%)
Effective Income Tax Rate Reconciliation, GILTI, percent	0.10%	(0.10%)
Other	1.50%	(0.30%)
Walter Energy accrual	(0.30%)	(5.80%)
Change in rate for deferred taxes	0.00%	2.10%
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent	(0.70%)	0.00%