Employer Sponsored Benefit Plans - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Interface
Defined Benefit Plan Disclosure [Line Items]
Contributions made by company to domestic pension plan	$ 300,000		$ 900,000
Interface | Minimum
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions during remainder of fiscal year	1,000,000.0		1,000,000.0
Interface | Maximum
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions during remainder of fiscal year	2,000,000.0		2,000,000.0
United States | Pension plan
Defined Benefit Plan Disclosure [Line Items]
Pre-tax settlement loss	25,500,000
Contributions made by company to domestic pension plan	$ 0	$ 3,000,000.0	$ 0	$ 4,200,000