EMPLOYER SPONSORED BENEFIT PLANS - Narrative (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Expected benefit from pension assets			$ 2,119,000	$ 2,601,000	$ 3,339,000
Estimated future employer contributions in next fiscal year			700,000
Employee benefit plans settlement expenses			$ 385,000	25,247,000	0
Assumed weighted rate of return (as a percent)			5.20%
Employer contributions to 401(k) plan			$ 3,800,000	3,700,000	2,900,000
Matching contribution of employees' gross pay (as a percent)			5.00%
Matching contribution of employees' gross pay, first 3% (as a percent)			100.00%
Matching contribution of employees' gross pay, remaining 2% (as a percent)			50.00%
United States
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer			$ 1,949,000	1,415,000
Payment for plan settlement			2,920,000	48,773,000
Outstanding plan obligation		$ 55,101,000	58,443,000	55,101,000	$ 102,679,000
Increase in OCI pension adjustment			300,000
Interface
Defined Benefit Plan Disclosure [Line Items]
Benefit expense since acquisition date			500,000	500,000
Interface | United States
Defined Benefit Plan Disclosure [Line Items]
Increase in OCI pension adjustment			2,200,000	300,000
Pension Plan | United States
Defined Benefit Plan Disclosure [Line Items]
Pre-tax settlement		(500,000)		25,700,000
Contributions by employer			0	0
Payment for plan settlement		$ 2,200,000
Outstanding plan obligation			$ 2,700,000
Employee benefit plans settlement expenses				$ 19,400,000
Pension Plan | ISS Pension Plan | United States
Defined Benefit Plan Disclosure [Line Items]
Pre-tax settlement	$ 400,000