Condensed Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Condensed Consolidated Statement of Other Comprehensive Income (Loss) [Abstract]
Net income	$ 14.5	$ 13.0	$ 23.3	$ 22.4
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustment	(1.3)	(0.8)	(6.9)	(1.1)
Pension liabilities adjustment	0.0	0.0	(0.2)	0.0
Net unrealized gain or loss on available-for-sale securities	0.0	2.3	0.0	3.4
Reclassification of adjustments included in net income [Abstract]
Periodic pension costs (included in compensation and benefits)	0.0	0.0	0.4	0.0
Reclassification adjustment for gains included in net income	0.0	0.0	0.4	0.0
Other comprehensive income (loss)	(1.3)	1.5	(6.7)	2.3
Comprehensive income	$ 13.2	$ 14.5	$ 16.6	$ 24.7