SCHEDULE I - CONDENSED STATEMENTS OF CASH FLOWS (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash Flows From Financing Activities [Abstract]
Proceeds from stock option exercises	$ 23.7	$ 22.7	$ 42.7
Cash dividends on common stock	(8.2)	0.0	0.0
Purchases of treasury stock	(736.8)	(2.1)	(18.6)
Purchase of shares from noncontrolling interests	0.0	(14.9)	0.0
Proceeds from sale of noncontrolling interests	0.0	11.9	0.0
Net increase in cash and cash equivalents	358.7	1,245.4	284.3
Cash and cash equivalents, beginning of year	1,750.9	505.5	221.2
Cash and cash equivalents, end of year	2,109.6	1,750.9	505.5
Parent Company
Cash Flows From Operating Activities [Abstract]
Net cash provided by (used in) operating activities	(9.7)	(15.1)	(15.1)
Cash Flows From Investing Activities [Abstract]
Advances to subsidiaries	731.0	(2.5)	(10.1)
Net cash used in investing activities from continuing operations	731.0	(2.5)	(10.1)
Cash Flows From Financing Activities [Abstract]
Proceeds from stock option exercises	23.7	22.7	42.8
Cash dividends on common stock	(8.2)	0.0	0.0
Purchases of treasury stock	(736.8)	(2.1)	(18.6)
Purchase of shares from noncontrolling interests	0.0	(14.9)	0.0
Proceeds from sale of noncontrolling interests	0.0	11.9	0.0
Net cash (used in) provided by financing activities from continuing operations	(721.3)	17.6	24.2
Net increase in cash and cash equivalents	0.0	0.0	(1.0)
Cash and cash equivalents, beginning of year	0.0	0.0	1.0
Cash and cash equivalents, end of year	$ 0.0	$ 0.0	$ 0.0

Amount of cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage. Excludes amount for disposal group and discontinued operations. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.

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Amount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.

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The cash outflow to reacquire common stock during the period.

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The cash outflow to acquire an agreement for an unconditional promise by the maker to pay the entity (holder) a definite sum of money at a future date. Such amount may include accrued interest receivable in accordance with the terms of the note. The note also may contain provisions including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among myriad other features and characteristics.

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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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