Amount of cost for defined contribution plan.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

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Amount of tax benefit from exercise of option under share-based payment arrangement.

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Amount of cash inflow from exercise of option under share-based payment arrangement.

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Amount of noncash expense for share-based payment arrangement.

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Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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Description of terms of share-based payment arrangement. Includes, but is not limited to, type of award or grantee and reason for issuance.

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Date the equity-based award expires, in CCYY-MM-DD format.

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Number of shares authorized for issuance under share-based payment arrangement.

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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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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Intrinsic value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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Intrinsic value of vested award under share-based payment arrangement. Excludes share and unit options.

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Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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EMPLOYEE COMPENSATION PLANS (NARRATIVE) (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions		1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 30, 2020	Feb. 29, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent				75.00%
Company Match on US Defined Contribution Plans				$ 6,700	$ 5,200	$ 5,700
Equity-based compensation expense				12,814	12,145	11,852
Total Tax Benefit Recognized for Equity-Based Compensation Expense				$ 4,200	3,700	6,800
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value				$ 40.10
Intrinsic Value of Non-Vested RSUs				$ 30,400
Fair Value of Shares Vested						0
Proceeds from exercise of stock options				0	208	2,150
Recognized Tax Benefit from Exercise of Stock Options				$ 0	0	0
2010 Plan [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Plan, Expiration Date	Mar. 30, 2020
Shares Authorized under Current Equity Compensation Plan				4.0
Shares Available for Issuance under Current Equity Compensation Plan				1.1
2020 Plan [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Shares Available for Issuance under Current Equity Compensation Plan		4.0
Cost of Services
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Equity-based compensation expense				$ 4,700	4,700	4,100
Selling General And Administrative Expenses [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Equity-based compensation expense				$ 8,100	7,400	7,800
Minimum \| 2010 Plan [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based Compensation Award Vesting Period				4 years
Minimum \| 2020 Plan [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based Compensation Award Vesting Period		3 years
Maximum \| 2010 Plan [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based Compensation Award Vesting Period				5 years
Maximum \| 2020 Plan [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based Compensation Award Vesting Period		5 years
Stock Options [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Intrinsic Value of Options Exercised					$ 156	$ 194
Restricted Stock Units (RSUs) [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Unrecognized Compensation Expense				$ 16,500
Requisite Service Period				1 year 3 months 18 days
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value				$ 40.10	$ 35.15	$ 29.56
Intrinsic Value of RSUs Vested				$ 12,500	$ 12,500	$ 10,600
Restricted Stock Units (RSUs) [Member] \| Executive Vice President [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Equity-based compensation expense						$ 100	$ 400
Performance Shares [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Equity-based compensation expense				$ 1,400
Performance Shares [Member] \| Minimum
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Description			$0.4 million
Performance Shares [Member] \| Maximum
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Description			$1.4 million