Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of tax benefit from exercise of stock options granted under share-based compensation arrangement.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Number of share instruments newly issued under a share-based compensation plan.

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Percentage of vesting of share-based compensation awards.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Share based compensation arrangement by share based payment award fair value assumptions risk free interest rate expected life.

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STOCK-BASED COMPENSATION PLANS - Narrative (FY) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 6.4	$ 2.6	$ 20.5	$ 14.5			$ 21.3	$ 20.8	$ 26.0
Tax benefits related to stock-based compensation plans							8.9	$ 14.9	$ 15.3
Unamortized compensation expense expected to be vested	35.4		35.4				$ 24.6
Recognized weighted average period, years							1 year 2 months 12 days
Risk-free interest rate, year							7 years
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	0.4		1.2				$ 1.7
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	2.3		5.0
Non-Vested Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense							7.0
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	2.3		$ 7.0				$ 4.6
Incentive Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period			3 years				3 years
Stock-based compensation expense	$ 1.2		$ 6.4				$ 6.5
Percentage of incentive stock awards expected to be vested and awarded of stocks granted							84.00%
Incentive Stock Awards \| Scenario Forecast as of December 31,2017 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of incentive stock awards expected to be vested and awarded of stocks granted					91.00%	77.00%
Incentive Stock Awards \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of incentive stock awards expected to be vested and awarded of stocks granted			0.00%				0.00%
Incentive Stock Awards \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of incentive stock awards expected to be vested and awarded of stocks granted			200.00%				200.00%
Directors Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares issued							881,192
Stock-based compensation expense							$ 1.5
Directors Plan \| Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Plan term, years							10 years
Shares authorized for grants							1,000,000
Award vesting period							3 years
Directors Plan \| Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period							1 year
Shares issued							16,500	16,972	11,256
Directors Plan \| Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period							1 year
2011 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for grant							3,192,453
Shares authorized for grants	3,800,000		3,800,000
2011 Plan \| Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Plan term, years			10 years				10 years
Award vesting period			4 years				4 years
2011 Plan \| Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period			4 years				4 years
2000 Plan \| Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Plan term, years			10 years				10 years
Award vesting period			4 years				4 years
2000 Plan \| Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period			4 years				4 years