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Aggregate dividends paid during the period for each share of common stock outstanding.

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Aggregate dividends declared during the period for each share of common stock outstanding.

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Amount of cash outflow in the form of ordinary dividends to common shareholders of the parent entity.

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Amount of cash outflow to satisfy grantee's tax withholding obligation for award under share-based payment arrangement.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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Equity impact of the value of stock that has been repurchased and retired during the period. The excess of the purchase price over par value can be charged against retained earnings (once the excess is fully allocated to additional paid in capital).

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Equity - Share Repurchases, Dividends, Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions			1 Months Ended	3 Months Ended						9 Months Ended
	Oct. 22, 2019	Oct. 23, 2018	Mar. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Share Repurchase Plan
Increase in authorized number of shares to be repurchased		5,000,000.0
Number of shares authorized by the Board of Directors to be repurchased under share repurchase plan				6,400,000						6,400,000
Number of shares authorized by the Board of Directors to be repurchased under share repurchase plan, expressed as a percentage of outstanding shares (as a percent)				10.00%						10.00%
Value of shares repurchased					$ 50.0		$ 80.1	$ 0.7	$ 49.3	$ 50.0
Value of shares repurchased											$ 130.7
Value of shares repurchased pending settlement											$ 0.6
Dividends
Common stock quarterly dividend per share (in dollars per share)	$ 0.55			$ 0.55	$ 0.55	$ 0.55	$ 0.50	$ 0.50	$ 0.50
Common stock dividend quarterly declared and paid per share (in dollars per share)				$ 0.55			$ 0.50			$ 1.65	$ 1.50
Dividends paid				$ 36.7			$ 35.9			$ 110.6	$ 108.5
Common Stock and Additional Paid in Capital
Share Repurchase Plan
Value of shares repurchased					$ 50.0		$ 80.1	$ 0.7	$ 49.3
Common Stock and Additional Paid-In (in Shares)
Payments made to tax authorities on employees' behalf										9.6	5.5
RSU's
Dividends
Dividend equivalents paid										$ 2.7	$ 2.0
Stock-Based Compensation
Vesting period (in years)										3 years
RSU's \| Service-based
Stock-Based Compensation
Vesting period (in years)			3 years
Changes
Granted (in shares)			294,190
Weighted Average Grant Date Fair Value
Granted (in dollars per shares)			$ 88.05
RSU's \| Performance-based
Stock-Based Compensation
Vesting period (in years)			3 years
Changes
Granted (in shares)			194,155
Weighted Average Grant Date Fair Value
Granted (in dollars per shares)			$ 88.05
Unvested RSUs
Changes
Unvested at the beginning of the period (in shares)						889,830				889,830
Granted (in shares)										488,345
Vested (in shares)										(3,837)
Cancelled or forfeited (in shares)										(10,318)
Unvested at the end of the period (in shares)				1,364,020						1,364,020
Shares reserved for future grants (all plans)				1,037,999						1,037,999
Weighted Average Grant Date Fair Value
Unvested at the beginning of the period (in dollars per share)						$ 82.05				$ 82.05
Granted (in dollars per shares)										88.05
Vested (in dollars per shares)										82.05
Cancelled or forfeited (in dollars per shares)										82.99
Unvested at the end of the period (in dollars per shares)				$ 84.19						$ 84.19