Variable Interest Entities (Narrative) (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Assets		$ 44,649.9	$ 44,291.2
Other investments		738.8	638.9
Maximum exposure to loss related to VIEs		253.9
Unfunded commitments		50.4
Consolidated investment entities
Variable Interest Entity [Line Items]
Assets	[1]	0.0	2,020.1
Collateralized Loan Obligation Funds
Variable Interest Entity [Line Items]
Fixed maturity securities and other investment		92.2
Collateralized Loan Obligation Funds | Subordinated Debt | Consolidated investment entities
Variable Interest Entity [Line Items]
Assets			77.4
Collateralized Loan Obligation Funds | Senior Debt | Consolidated investment entities
Variable Interest Entity [Line Items]
Assets			21.1
Real estate fund
Variable Interest Entity [Line Items]
Other investments		43.0
Real estate fund | Consolidated investment entities
Variable Interest Entity [Line Items]
Assets			88.3
Commercial Mortgage Loan Securitization
Variable Interest Entity [Line Items]
Maximum exposure to loss related to VIEs		$ 19.9	$ 19.1

[1] The following table presents information on assets and liabilities related to consolidated investment entities as of December 31, 2019. During the third quarter of 2020, the Company sold its collateralized loan obligation asset management platform and outsourced its real estate asset management, which resulted in the deconsolidation of the consolidated investment entities. Refer to Notes 4 and 9 for additional information. December 31, 2019AssetsCash and cash equivalents$32.9 Investments, at fair value1,957.9 Other receivables29.3 Total assets$2,020.1 LiabilitiesCollateralized loan obligation notes, at fair value$1,603.1 Other liabilities83.9 Total liabilities$1,687.0