Segment Information - Percentage of Total Sales by Product Group (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue from External Customer [Line Items]
Revenues	$ 314,438	$ 349,675	$ 655,583	$ 675,713
Breathing Apparatus
Revenue from External Customer [Line Items]
Revenues	75,864	74,907	151,708	150,354
Fixed Gas & Flame Detection
Revenue from External Customer [Line Items]
Revenues	65,385	70,310	135,296	130,709
Firefighter Helmets & Protective Apparel
Revenue from External Customer [Line Items]
Revenues	40,337	48,799	82,884	92,376
Portable Gas Detection
Revenue from External Customer [Line Items]
Revenues	28,385	42,343	65,933	83,069
Industrial Head Protection
Revenue from External Customer [Line Items]
Revenues	30,601	38,921	69,437	74,665
Fall Protection
Revenue from External Customer [Line Items]
Revenues	21,660	31,629	49,087	61,756
Other (a)
Revenue from External Customer [Line Items]
Revenues	$ 52,206	$ 42,766	$ 101,238	$ 82,784
Sales
Revenue from External Customer [Line Items]
Concentration risk percentage	100.00%	100.00%	100.00%	100.00%
Sales | Breathing Apparatus
Revenue from External Customer [Line Items]
Concentration risk percentage	24.00%	22.00%	23.00%	22.00%
Sales | Fixed Gas & Flame Detection
Revenue from External Customer [Line Items]
Concentration risk percentage	21.00%	20.00%	21.00%	19.00%
Sales | Firefighter Helmets & Protective Apparel
Revenue from External Customer [Line Items]
Concentration risk percentage	13.00%	14.00%	13.00%	14.00%
Sales | Portable Gas Detection
Revenue from External Customer [Line Items]
Concentration risk percentage	9.00%	12.00%	10.00%	12.00%
Sales | Industrial Head Protection
Revenue from External Customer [Line Items]
Concentration risk percentage	10.00%	11.00%	11.00%	12.00%
Sales | Fall Protection
Revenue from External Customer [Line Items]
Concentration risk percentage	7.00%	9.00%	7.00%	9.00%
Sales | Other (a)
Revenue from External Customer [Line Items]
Concentration risk percentage	16.00%	12.00%	15.00%	12.00%
Americas
Revenue from External Customer [Line Items]
Revenues	$ 204,231	$ 231,389	$ 435,484	$ 445,076
Americas | Breathing Apparatus
Revenue from External Customer [Line Items]
Revenues	50,269	50,584	102,962	101,489
Americas | Fixed Gas & Flame Detection
Revenue from External Customer [Line Items]
Revenues	36,742	39,118	77,989	72,048
Americas | Firefighter Helmets & Protective Apparel
Revenue from External Customer [Line Items]
Revenues	33,744	39,091	68,857	74,155
Americas | Portable Gas Detection
Revenue from External Customer [Line Items]
Revenues	17,201	33,844	48,061	55,458
Americas | Industrial Head Protection
Revenue from External Customer [Line Items]
Revenues	20,506	25,045	44,850	58,258
Americas | Fall Protection
Revenue from External Customer [Line Items]
Revenues	11,381	18,720	29,076	36,680
Americas | Other (a)
Revenue from External Customer [Line Items]
Revenues	$ 34,388	$ 24,987	$ 63,689	$ 46,988
Americas | Sales
Revenue from External Customer [Line Items]
Concentration risk percentage	100.00%	100.00%	100.00%	100.00%
Americas | Sales | Breathing Apparatus
Revenue from External Customer [Line Items]
Concentration risk percentage	25.00%	22.00%	24.00%	23.00%
Americas | Sales | Fixed Gas & Flame Detection
Revenue from External Customer [Line Items]
Concentration risk percentage	18.00%	17.00%	18.00%	16.00%
Americas | Sales | Firefighter Helmets & Protective Apparel
Revenue from External Customer [Line Items]
Concentration risk percentage	16.00%	17.00%	16.00%	17.00%
Americas | Sales | Portable Gas Detection
Revenue from External Customer [Line Items]
Concentration risk percentage	8.00%	13.00%	11.00%	12.00%
Americas | Sales | Industrial Head Protection
Revenue from External Customer [Line Items]
Concentration risk percentage	10.00%	12.00%	10.00%	13.00%
Americas | Sales | Fall Protection
Revenue from External Customer [Line Items]
Concentration risk percentage	6.00%	8.00%	7.00%	8.00%
Americas | Sales | Other (a)
Revenue from External Customer [Line Items]
Concentration risk percentage	17.00%	11.00%	14.00%	11.00%
International
Revenue from External Customer [Line Items]
Revenues	$ 110,207	$ 118,286	$ 220,099	$ 230,637
International | Breathing Apparatus
Revenue from External Customer [Line Items]
Revenues	25,595	24,323	48,746	48,865
International | Fixed Gas & Flame Detection
Revenue from External Customer [Line Items]
Revenues	28,643	31,192	57,307	58,661
International | Firefighter Helmets & Protective Apparel
Revenue from External Customer [Line Items]
Revenues	6,593	9,708	14,027	18,221
International | Portable Gas Detection
Revenue from External Customer [Line Items]
Revenues	11,184	8,499	17,872	27,611
International | Industrial Head Protection
Revenue from External Customer [Line Items]
Revenues	10,095	13,876	24,587	16,407
International | Fall Protection
Revenue from External Customer [Line Items]
Revenues	10,279	12,909	20,011	25,076
International | Other (a)
Revenue from External Customer [Line Items]
Revenues	$ 17,818	$ 17,779	$ 37,549	$ 35,796
International | Sales
Revenue from External Customer [Line Items]
Concentration risk percentage	100.00%	100.00%	100.00%	100.00%
International | Sales | Breathing Apparatus
Revenue from External Customer [Line Items]
Concentration risk percentage	23.00%	21.00%	22.00%	21.00%
International | Sales | Fixed Gas & Flame Detection
Revenue from External Customer [Line Items]
Concentration risk percentage	26.00%	26.00%	26.00%	25.00%
International | Sales | Firefighter Helmets & Protective Apparel
Revenue from External Customer [Line Items]
Concentration risk percentage	6.00%	8.00%	7.00%	8.00%
International | Sales | Portable Gas Detection
Revenue from External Customer [Line Items]
Concentration risk percentage	10.00%	7.00%	8.00%	12.00%
International | Sales | Industrial Head Protection
Revenue from External Customer [Line Items]
Concentration risk percentage	9.00%	12.00%	11.00%	7.00%
International | Sales | Fall Protection
Revenue from External Customer [Line Items]
Concentration risk percentage	9.00%	11.00%	9.00%	11.00%
International | Sales | Other (a)
Revenue from External Customer [Line Items]
Concentration risk percentage	17.00%	15.00%	17.00%	16.00%