Segment reporting (Details 4) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
REVENUE	$ 304.9	$ 306.1	$ 257.3	$ 293.0	$ 290.0	$ 299.7	$ 282.7	$ 298.7	$ 1,161.3	$ 1,171.1	$ 1,101.5
Long-lived assets	211.5				226.3				211.5	226.3
Germany
Revenues from External Customers and Long-Lived Assets [Line Items]
REVENUE									174.9	200.3	198.6
Long-lived assets	157.0				192.6				157.0	192.6
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
REVENUE									384.7	352.4	336.7
Long-lived assets	26.3				6.7				26.3	6.7
Rest of World
Revenues from External Customers and Long-Lived Assets [Line Items]
REVENUE									601.7	618.4	$ 566.2
Long-lived assets	$ 28.2				$ 27.0				$ 28.2	$ 27.0