Represents the number of separate incentive compensation programs within a incentive compensation plan.

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Period which an employee's right to exercise an award.

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Represents the number of share based compensation plans utilized by the entity.

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of tax benefit from exercise of option 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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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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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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Number of additional shares authorized for issuance under share-based payment arrangement.

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

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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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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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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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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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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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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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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Purchase price of common stock expressed as a percentage of its fair value.

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Number of share options (or share units) exercised during the current period.

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SHARE-BASED AWARDS - SUMMARY (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) plan $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($)
Share-based expense (net of estimated forfeitures)
Total share-based expense	$ 18,800	$ 11,300	$ 12,100
Intrinsic value of options exercised	5,800	500	500
Tax benefit realized upon option exercise	3,300	2,000	2,700
Fair value of stock vested	13,100	$ 8,200	$ 10,800
Stock options
Share-based expense (net of estimated forfeitures)
Unrecognized compensation cost	$ 0
Weighted average exercise price
Outstanding, weighted average exercise price, beginning of period (in dollars per share) \| $ / shares	$ 22.30
Exercised, weighted average exercise price (in dollars per share) \| $ / shares	22.31
Outstanding, weighted average exercise price, end of period (in dollars per share) \| $ / shares	20.84	$ 22.30
Exercisable, weighted average exercise price, end of period (in dollars per share) \| $ / shares	$ 20.84
Outstanding, weighted average contractual life, end of period	1 month 6 days
Exercisable, weighted average contractual life, end of period	1 month 6 days
Outstanding, aggregate intrinsic value, end of period (in dollars)	$ 35
Exercisable, aggregate intrinsic value, end of period (in dollars)	35
Non-vested restricted stock units and performance-based equity awards
Share-based expense (net of estimated forfeitures)
Unrecognized compensation cost	$ 17,700
Unrecognized compensation cost, weighted average period for recognition	1 year 8 months 12 days
Restricted Stock Units
Share-based compensation
Options granted, weighted average grant-date fair value (in dollars per share) \| $ / shares	$ 38.68
2016 Plan
Share-based compensation
Common stock initially available for future issuance (in shares) \| shares	2,500
Additional shares authorized for issuance \| shares	0
Number of separate incentive compensation programs \| plan	4
Number of share based compensation plans within the entity's incentive compensation programs \| plan	3
2016 Plan \| Discretionary Grant Program
Share-based compensation
Minimum exercise price as a percentage of fair market value of common stock	100.00%
Exercisable period	3 years
Expiration Term	10 years
2016 Plan \| Time-Based Restricted Stock Units \| Stock Issuance Program
Share-based compensation
Vesting period of awards granted	3 years
2016 Plan \| Time-Based Restricted Stock Units \| Automatic Grant Program
Share-based compensation
Vesting period of awards granted	1 year
2016 Plan \| Performance-Based Restricted Stock Units \| Stock Issuance Program
Share-based compensation
Vesting period of awards granted	3 years
2007 Plan \| Stock options
Activity in the entity's stock option plans
Outstanding, beginning of period (in shares) \| shares	173
Exercised (in shares) \| shares	(172)
Outstanding, end of period (in shares) \| shares	1	173
Exercisable, end of period (in shares) \| shares	1