Receivables from customers, net and notes receivable, net - Exim Bank Notes Receivable (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Insured short-term notes receivable		$ 2.1	$ 5.0
Obligations for participation rights		$ 2.1	$ 4.6
Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Short Term Notes Receivable Outstanding Balance Threshold, Percentage	90.00%	90.00%
Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Short Term Notes Receivable Outstanding Balance Threshold, Percentage	98.00%	98.00%