Employer Sponsored Benefit Plans - Narrative (Details) - USD ($)	3 Months Ended	4 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Estimated future employer contributions in next fiscal year	$ 2,400,000		$ 2,400,000
Assumed weighted rate of return (as a percent)			5.20%
Defined Contribution Plan:
Employer Contributions to 401(k) Plan			$ 3,700,000	$ 2,900,000	$ 2,600,000
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			$ 1,415,000	7,500,000
Payment for plan settlement			48,773,000	0
Outstanding plan obligation	55,101,000	$ 102,679,000	55,101,000	102,679,000	$ 51,882,000
Pension plan liability	11,163,000	15,227,000	11,163,000	15,227,000
Accumulated other comprehensive loss, net of tax	2,579,000	21,850,000	2,579,000	21,850,000
Increase in OCI pension adjustment			19,400,000	1,800,000
Funded (unfunded) status of plan	(11,163,000)	(15,227,000)	(11,163,000)	(15,227,000)
United States | Minimum
Defined Benefit Plan Disclosure [Line Items]
Future amortization of gain (loss)	400,000		400,000
United States | Maximum
Defined Benefit Plan Disclosure [Line Items]
Future amortization of gain (loss)	600,000		600,000
Foreign Plan
Defined Benefit Plan Disclosure [Line Items]
Pension plan liability	5,200,000	4,700,000	5,200,000	4,700,000
Accumulated other comprehensive loss, net of tax	900,000	400,000	900,000	400,000
Interface | United States
Defined Benefit Plan Disclosure [Line Items]
Increase in OCI pension adjustment			300,000	1,800,000
Postemployment Retirement Benefits | Interface | United States
Defined Benefit Plan Disclosure [Line Items]
Pension plan liability	3,600,000	4,100,000	3,600,000	4,100,000
Benefit expense since acquisition date		100,000	100,000
Benefit payments since acquisition date		$ 100,000	200,000
Pension Plan | United States
Defined Benefit Plan Disclosure [Line Items]
Pre-tax settlement			25,700,000
Contributions by employer			0
Pension Plan | United States | Minimum
Defined Benefit Plan Disclosure [Line Items]
Estimated future employer contributions in next fiscal year	700,000		700,000
Pension Plan | United States | Maximum
Defined Benefit Plan Disclosure [Line Items]
Estimated future employer contributions in next fiscal year	900,000		900,000
Pension Plan | Interface Pension Plans | United States
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer			1,400,000
Multiemployer Plans, Pension | Pension Plan | United States
Defined Benefit Plan Disclosure [Line Items]
Pre-tax settlement			500,000
Contributions by employer			$ 0	$ 0
Payment for plan settlement	$ 2,200,000
Outstanding plan obligation						$ 2,700,000