Income Taxes - Effective Rate Reconciliation (Details)	12 Months Ended
	Sep. 30, 2017 Rate	Sep. 30, 2016 Rate	Sep. 30, 2015 Rate
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate	35.00%	35.00%	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes	(2.60%)	1.30%	1.80%
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential	11.50%	(11.00%)	(11.10%)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Meals and Entertainment	3.60%	0.80%	0.50%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other	8.10%	1.90%	2.10%
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent	0.00%	(3.00%)	0.00%
Effective Income Tax Rate Reconciliation, Deductions, Other	(0.60%)	(0.30%)	(0.10%)
Effective Income Tax Rate, Continuing Operations	57.70%	25.00%	28.70%
Foreign Tax Authority [Member]
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance	(1.40%)	(0.30%)	(0.10%)
State and Local Jurisdiction [Member]
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance	4.10%	0.00%	0.60%