Summary of Significant Accounting Policies Summary of Significant Accounting Details, Noncontrolling Interest (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Redeemable Noncontrolling Interest	$ 7.8	$ 8.6	$ 0.0	$ 3.8
Noncontrolling Interest, Increase from Business Combination		8.4
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests			$ (3.8)
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest	(0.3)	0.2
Payments to Noncontrolling Interests	(0.5)
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	$ 430.8	404.2
Additional Paid-in Capital [Member]
Redeemable Noncontrolling Interest, Equity, Redemption Value		$ 2.3

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Amount of investment in equity method investee and investment in and advance to affiliate.

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Decrease in noncontrolling interest (for example, but not limited to, redeeming or purchasing the interests of noncontrolling shareholders, issuance of shares (interests) by the non-wholly owned subsidiary to the parent entity for other than cash, and a buyback of shares (interest) by the non-wholly owned subsidiary from the noncontrolling interests).

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Amount of Net Income (Loss) attributable to redeemable noncontrolling interest.

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Amount of increase in noncontrolling interest from a business combination.

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Amount of cash outflow to a noncontrolling interest. Includes, but not limited to, reduction of noncontrolling interest ownership. Excludes dividends paid to the noncontrolling interest.

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As of the reporting date, the aggregate carrying amount of all noncontrolling interests which are redeemable by the (parent) entity (1) at a fixed or determinable price on a fixed or determinable date, (2) at the option of the holder of the noncontrolling interest, or (3) upon occurrence of an event that is not solely within the control of the (parent) entity. This item includes noncontrolling interest holder's ownership (or holders' ownership) regardless of the type of equity interest (common, preferred, other) including all potential organizational (legal) forms of the investee entity.

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Redemption value, as if currently redeemable, of redeemable noncontrolling interest classified as temporary equity and the election has been made to accrete changes in redemption value to the earliest redemption date.

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