Business combinations (Schedule of the Valuation of the Intangible Assets Acquired) (Details) - Ascend Management Innovations LLC $ in Thousands	6 Months Ended
	Mar. 31, 2017 USD ($)
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	$ 22,300
Customer relationships
Business Acquisition [Line Items]
Finite-lived intangible asset, useful life	19 years
Finite-lived intangible assets acquired	$ 20,400
Trade Names
Business Acquisition [Line Items]
Finite-lived intangible asset, useful life	8 years
Finite-lived intangible assets acquired	$ 1,700
Technology-Based Intangible Assets
Business Acquisition [Line Items]
Finite-lived intangible asset, useful life	1 year
Finite-lived intangible assets acquired	$ 200