Accounting Policies and Pronouncements Accounting Policies and Pronouncments (Details) $ in Millions	9 Months Ended
	Sep. 30, 2016 USD ($)
Accounting Standards Update 2015-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deconsolidated assets of certain investment partnerships	$ 0.0
Effective as of January 1, 2016 | Accounting Standards Update 2015-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deconsolidated assets of certain investment partnerships	9.4
Actual impact as of period end | Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefits recorded as additional paid-in-capital	$ 7.0