Segment Information - Percentage of Total Sales by Product Group (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue from External Customer [Line Items]
Revenues	$ 308,428	$ 341,145
Breathing Apparatus
Revenue from External Customer [Line Items]
Revenues	69,644	75,844
Fixed Gas & Flame Detection
Revenue from External Customer [Line Items]
Revenues	60,119	69,911
Firefighter Helmets & Protective Apparel
Revenue from External Customer [Line Items]
Revenues	46,010	42,547
Portable Gas Detection
Revenue from External Customer [Line Items]
Revenues	37,429	41,052
Industrial Head Protection
Revenue from External Customer [Line Items]
Revenues	32,696	35,332
Fall Protection
Revenue from External Customer [Line Items]
Revenues	26,067	27,428
Other
Revenue from External Customer [Line Items]
Revenues	$ 36,463	$ 49,031
Sales
Revenue from External Customer [Line Items]
Concentration risk percentage	100.00%	100.00%
Sales | Breathing Apparatus
Revenue from External Customer [Line Items]
Concentration risk percentage	23.00%	22.00%
Sales | Fixed Gas & Flame Detection
Revenue from External Customer [Line Items]
Concentration risk percentage	19.00%	21.00%
Sales | Firefighter Helmets & Protective Apparel
Revenue from External Customer [Line Items]
Concentration risk percentage	15.00%	12.00%
Sales | Portable Gas Detection
Revenue from External Customer [Line Items]
Concentration risk percentage	12.00%	12.00%
Sales | Industrial Head Protection
Revenue from External Customer [Line Items]
Concentration risk percentage	11.00%	10.00%
Sales | Fall Protection
Revenue from External Customer [Line Items]
Concentration risk percentage	8.00%	8.00%
Sales | Other
Revenue from External Customer [Line Items]
Concentration risk percentage	12.00%	15.00%
Americas
Revenue from External Customer [Line Items]
Revenues	$ 208,340	$ 231,253
Americas | Breathing Apparatus
Revenue from External Customer [Line Items]
Revenues	48,798	52,693
Americas | Fixed Gas & Flame Detection
Revenue from External Customer [Line Items]
Revenues	36,277	41,247
Americas | Firefighter Helmets & Protective Apparel
Revenue from External Customer [Line Items]
Revenues	34,988	35,113
Americas | Portable Gas Detection
Revenue from External Customer [Line Items]
Revenues	25,702	27,648
Americas | Industrial Head Protection
Revenue from External Customer [Line Items]
Revenues	25,111	27,555
Americas | Fall Protection
Revenue from External Customer [Line Items]
Revenues	15,672	17,697
Americas | Other
Revenue from External Customer [Line Items]
Revenues	$ 21,792	$ 29,300
Americas | Sales
Revenue from External Customer [Line Items]
Concentration risk percentage	100.00%	100.00%
Americas | Sales | Breathing Apparatus
Revenue from External Customer [Line Items]
Concentration risk percentage	23.00%	23.00%
Americas | Sales | Fixed Gas & Flame Detection
Revenue from External Customer [Line Items]
Concentration risk percentage	17.00%	18.00%
Americas | Sales | Firefighter Helmets & Protective Apparel
Revenue from External Customer [Line Items]
Concentration risk percentage	17.00%	15.00%
Americas | Sales | Portable Gas Detection
Revenue from External Customer [Line Items]
Concentration risk percentage	12.00%	12.00%
Americas | Sales | Industrial Head Protection
Revenue from External Customer [Line Items]
Concentration risk percentage	12.00%	12.00%
Americas | Sales | Fall Protection
Revenue from External Customer [Line Items]
Concentration risk percentage	8.00%	8.00%
Americas | Sales | Other
Revenue from External Customer [Line Items]
Concentration risk percentage	11.00%	12.00%
International
Revenue from External Customer [Line Items]
Revenues	$ 100,088	$ 109,892
International | Breathing Apparatus
Revenue from External Customer [Line Items]
Revenues	20,846	23,151
International | Fixed Gas & Flame Detection
Revenue from External Customer [Line Items]
Revenues	23,842	28,664
International | Firefighter Helmets & Protective Apparel
Revenue from External Customer [Line Items]
Revenues	11,022	7,434
International | Portable Gas Detection
Revenue from External Customer [Line Items]
Revenues	11,727	13,404
International | Industrial Head Protection
Revenue from External Customer [Line Items]
Revenues	7,585	7,777
International | Fall Protection
Revenue from External Customer [Line Items]
Revenues	10,395	9,731
International | Other
Revenue from External Customer [Line Items]
Revenues	$ 14,671	$ 19,731
International | Sales
Revenue from External Customer [Line Items]
Concentration risk percentage	100.00%	100.00%
International | Sales | Breathing Apparatus
Revenue from External Customer [Line Items]
Concentration risk percentage	21.00%	21.00%
International | Sales | Fixed Gas & Flame Detection
Revenue from External Customer [Line Items]
Concentration risk percentage	24.00%	26.00%
International | Sales | Firefighter Helmets & Protective Apparel
Revenue from External Customer [Line Items]
Concentration risk percentage	11.00%	7.00%
International | Sales | Portable Gas Detection
Revenue from External Customer [Line Items]
Concentration risk percentage	12.00%	12.00%
International | Sales | Industrial Head Protection
Revenue from External Customer [Line Items]
Concentration risk percentage	8.00%	7.00%
International | Sales | Fall Protection
Revenue from External Customer [Line Items]
Concentration risk percentage	10.00%	9.00%
International | Sales | Other
Revenue from External Customer [Line Items]
Concentration risk percentage	14.00%	18.00%