Variable Interest Entities (Details) - Variable Interest Entity, Not Primary Beneficiary [Member] - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Other Assets [Member]
Variable Interest Entity [Line Items]
Variable interest entities, investments, carrying value	$ 22.8	$ 25.9
Accounts Payable and Accrued Liabilities [Member]
Variable Interest Entity [Line Items]
Variable interest entities, unfunded commitments	14.0	16.5
Other Investments [Member]
Variable Interest Entity [Line Items]
Variable interest entities, investments, carrying value	12.3	12.1
Unfunded Loan Commitment [Member]
Variable Interest Entity [Line Items]
Variable interest entities, total exposure of other investments including unfunded commitments	$ 19.9	$ 19.0