Employer Sponsored Benefit Plans - Narrative (Details)	3 Months Ended
	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) plan_participant active_employee
Interface
Defined Benefit Plan Disclosure [Line Items]
Contributions made by company to domestic pension plan	$ 600,000
Interface | Minimum
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions during remainder of fiscal year	1,000,000
Interface | Maximum
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions during remainder of fiscal year	2,000,000
United States | Minimum
Defined Benefit Plan Disclosure [Line Items]
Estimated future amortization of gain (loss)			$ (29,000,000)
United States | Maximum
Defined Benefit Plan Disclosure [Line Items]
Estimated future amortization of gain (loss)			$ (33,000,000)
United States | Pension plan
Defined Benefit Plan Disclosure [Line Items]
Number of plan participants | plan_participant			900
Number of active employee plan participants | active_employee			200
Contributions made by company to domestic pension plan	$ 0	$ 1,200,000
United States | Pension plan | Minimum
Defined Benefit Plan Disclosure [Line Items]
Estimated future employer contributions in next fiscal year			$ 2,000,000
United States | Pension plan | Maximum
Defined Benefit Plan Disclosure [Line Items]
Estimated future employer contributions in next fiscal year			$ 4,000,000