Investments - Schedule of Other Invested Assets (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Summary of Investment Holdings [Line Items]
Measurement Alternative	$ 0.0	$ 1.6
Equity Method	71.1	70.9
Common Equity
Summary of Investment Holdings [Line Items]
Measurement Alternative	0.0	0.0
Equity Method	2.3	2.1
Preferred Equity
Summary of Investment Holdings [Line Items]
Measurement Alternative	0.0	1.6
Equity Method	8.0	9.6
Other
Summary of Investment Holdings [Line Items]
Measurement Alternative	0.0	0.0
Equity Method	$ 60.8	$ 59.2

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=109237563&loc=d3e33749-111570

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 25
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8813-108599

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant