Accounting Policies (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Net waivers	$ 0.6
Payments for Repurchase of Common Stock	52.5	$ 36.6
Accounting Standards Update 2016-09 [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Excess Tax Benefit from Share-based Compensation, Operating Activities	1.3
Waiver [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Management and administrative fees	$ 1.7
Change in third party distribution service and advisory fee	62.00%