Income Taxes Income Tax Rate Reconciliation (Details)	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. federal statutory income tax rate	35.00%	35.00%	35.00%	35.00%
Adjustments to reconcile to the effective tax rate:
State tax rate change	14.90%	0.00%	6.40%	0.00%
State income taxes, net of federal benefit	3.70%	4.40%	3.80%	4.40%
Tax benefits from stock compensation	(30.00%)	(4.20%)	(17.20%)	(3.20%)
U.S. manufacturing deduction	(4.90%)	(3.30%)	(4.10%)	(3.30%)
Tax credits	(7.20%)	(0.60%)	(3.50%)	(0.60%)
Other	1.50%	0.90%	1.30%	(2.10%)
Effective income tax rate	13.00%	32.20%	21.70%	30.20%