Variable Interest Entities (Variable Interest Entity, Consolidated, Carrying Amount, Assets) (Details) - Variable Interest Entity, Not Primary Beneficiary [Member] - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Other Assets [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	$ 43.5	$ 29.1
Accounts Payable and Accrued Liabilities [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	15.5	10.4
Other Investments [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	20.3	17.6
Unfunded Loan Commitment [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 54.5	$ 31.0