Segment Information - Percentage of Total Sales by Product Group (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue from External Customer [Line Items]
Revenues	$ 341,289	$ 314,438	$ 649,717	$ 655,583
Breathing Apparatus
Revenue from External Customer [Line Items]
Revenues	76,659	75,864	146,304	151,708
Fixed Gas & Flame Detection
Revenue from External Customer [Line Items]
Revenues	64,920	65,385	125,039	135,296
Firefighter Helmets & Protective Apparel
Revenue from External Customer [Line Items]
Revenues	53,121	40,337	99,131	82,884
Portable Gas Detection
Revenue from External Customer [Line Items]
Revenues	38,820	28,385	76,249	69,437
Industrial Head Protection
Revenue from External Customer [Line Items]
Revenues	38,155	30,601	70,851	65,933
Fall Protection
Revenue from External Customer [Line Items]
Revenues	30,809	21,660	56,876	49,087
Other
Revenue from External Customer [Line Items]
Revenues	$ 38,805	$ 52,206	$ 75,267	$ 101,238
Revenue Benchmark | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	100.00%	100.00%	100.00%	100.00%
Revenue Benchmark | Breathing Apparatus | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	22.00%	24.00%	23.00%	23.00%
Revenue Benchmark | Fixed Gas & Flame Detection | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	19.00%	21.00%	19.00%	21.00%
Revenue Benchmark | Firefighter Helmets & Protective Apparel | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	16.00%	13.00%	15.00%	13.00%
Revenue Benchmark | Portable Gas Detection | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	11.00%	9.00%	12.00%	11.00%
Revenue Benchmark | Industrial Head Protection | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	11.00%	10.00%	11.00%	10.00%
Revenue Benchmark | Fall Protection | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	9.00%	7.00%	9.00%	7.00%
Revenue Benchmark | Other | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	12.00%	16.00%	11.00%	15.00%
Americas
Revenue from External Customer [Line Items]
Revenues	$ 217,707	$ 204,231	$ 426,046	$ 435,484
Americas | Breathing Apparatus
Revenue from External Customer [Line Items]
Revenues	51,436	50,269	100,234	102,962
Americas | Fixed Gas & Flame Detection
Revenue from External Customer [Line Items]
Revenues	36,950	36,742	73,227	77,989
Americas | Firefighter Helmets & Protective Apparel
Revenue from External Customer [Line Items]
Revenues	36,424	33,744	71,413	68,857
Americas | Portable Gas Detection
Revenue from External Customer [Line Items]
Revenues	25,393	17,201	51,095	44,850
Americas | Industrial Head Protection
Revenue from External Customer [Line Items]
Revenues	28,820	20,506	53,931	48,061
Americas | Fall Protection
Revenue from External Customer [Line Items]
Revenues	17,677	11,381	33,349	29,076
Americas | Other
Revenue from External Customer [Line Items]
Revenues	$ 21,007	$ 34,388	$ 42,797	$ 63,689
Americas | Revenue Benchmark | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	100.00%	100.00%	100.00%	100.00%
Americas | Revenue Benchmark | Breathing Apparatus | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	24.00%	25.00%	24.00%	24.00%
Americas | Revenue Benchmark | Fixed Gas & Flame Detection | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	17.00%	18.00%	17.00%	18.00%
Americas | Revenue Benchmark | Firefighter Helmets & Protective Apparel | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	17.00%	16.00%	17.00%	16.00%
Americas | Revenue Benchmark | Portable Gas Detection | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	12.00%	8.00%	12.00%	10.00%
Americas | Revenue Benchmark | Industrial Head Protection | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	13.00%	10.00%	13.00%	11.00%
Americas | Revenue Benchmark | Fall Protection | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	8.00%	6.00%	8.00%	7.00%
Americas | Revenue Benchmark | Other | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	9.00%	17.00%	9.00%	14.00%
International
Revenue from External Customer [Line Items]
Revenues	$ 123,582	$ 110,207	$ 223,671	$ 220,099
International | Breathing Apparatus
Revenue from External Customer [Line Items]
Revenues	25,223	25,595	46,069	48,746
International | Fixed Gas & Flame Detection
Revenue from External Customer [Line Items]
Revenues	27,970	28,643	51,811	57,307
International | Firefighter Helmets & Protective Apparel
Revenue from External Customer [Line Items]
Revenues	16,697	6,593	27,719	14,027
International | Portable Gas Detection
Revenue from External Customer [Line Items]
Revenues	13,427	11,184	25,154	24,587
International | Industrial Head Protection
Revenue from External Customer [Line Items]
Revenues	9,335	10,095	16,920	17,872
International | Fall Protection
Revenue from External Customer [Line Items]
Revenues	13,132	10,279	23,526	20,011
International | Other
Revenue from External Customer [Line Items]
Revenues	$ 17,798	$ 17,818	$ 32,472	$ 37,549
International | Revenue Benchmark | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	100.00%	100.00%	100.00%	100.00%
International | Revenue Benchmark | Breathing Apparatus | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	20.00%	23.00%	21.00%	22.00%
International | Revenue Benchmark | Fixed Gas & Flame Detection | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	23.00%	26.00%	23.00%	26.00%
International | Revenue Benchmark | Firefighter Helmets & Protective Apparel | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	14.00%	6.00%	12.00%	7.00%
International | Revenue Benchmark | Portable Gas Detection | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	11.00%	10.00%	11.00%	11.00%
International | Revenue Benchmark | Industrial Head Protection | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	8.00%	9.00%	8.00%	8.00%
International | Revenue Benchmark | Fall Protection | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	11.00%	9.00%	11.00%	9.00%
International | Revenue Benchmark | Other | Product Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage	13.00%	17.00%	14.00%	17.00%