Assets and Liabilities, at Fair Value - Contingent Consideration (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Change in fair value of contingent consideration for acquisitions	$ 0.0	$ 0.2
Contingent Consideration [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Change in fair value of contingent consideration for acquisitions	$ 0.1	$ 0.2	$ 0.2