Investments Components of Equity Realized Gains (Losses) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Components of Equity Realized Gains (Losses) [Line Items]
Equity Securities, FV-NI, Realized Gain (Loss)	$ 86.7	$ 265.1
Equity Securities, FV-NI, Unrealized Gain (Loss)	739.9	(497.5)
Equity securities
Components of Equity Realized Gains (Losses) [Line Items]
Equity Securities, FV-NI, Gain (Loss)	826.6	(232.4)
Equity Securities, FV-NI, Realized Gain (Loss)	86.7	265.1
Equity Securities, FV-NI, Unrealized Gain (Loss)	$ 739.9	$ (497.5)

[Line Items] for Components of Equity Realized Gains (Losses) recorded during the period, including gains (losses) on security sales and holding period gains (losses) on securities held at the end of the period.

No definition available.

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- Definition

Amount of unrealized and realized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117546-209714

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Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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