Condensed Financial Information of Registrant (Parent Company) - Narrative (Details)	12 Months Ended
	Sep. 30, 2017 USD ($)
Flaga
Guarantee Obligations
Amount of floating to fixed rate interest rate swaps at Flaga	$ 600,000
Parent Company
Guarantee Obligations
Surety bonds indemnified	88,900,000
Maximum amount authorized to guarantee obligations to suppliers and customers	500,000,000
Current carrying value	$ 432,500,000