Net Revenues - Summary of Disaggregated Net Revenues (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Net revenues	$ 1,047	$ 958	$ 2,828	$ 2,705
United States [Member]
Disaggregation of Revenue [Line Items]
Net revenues	955	901	2,550	2,557
Canada and Europe [Member]
Disaggregation of Revenue [Line Items]
Net revenues	92	57	278	148
Safety Services [Member]
Disaggregation of Revenue [Line Items]
Net revenues	533	404	1,511	1,199
Safety Services [Member] \| United States [Member]
Disaggregation of Revenue [Line Items]
Net revenues	452	361	1,257	1,074
Safety Services [Member] \| Canada and Europe [Member]
Disaggregation of Revenue [Line Items]
Net revenues	81	43	254	125
Specialty Services [Member]
Disaggregation of Revenue [Line Items]
Net revenues	436	400	1,172	1,049
Specialty Services [Member] \| United States [Member]
Disaggregation of Revenue [Line Items]
Net revenues	436	400	1,172	1,049
Industrial Services [Member]
Disaggregation of Revenue [Line Items]
Net revenues	103	158	196	468
Industrial Services [Member] \| United States [Member]
Disaggregation of Revenue [Line Items]
Net revenues	92	144	172	445
Industrial Services [Member] \| Canada and Europe [Member]
Disaggregation of Revenue [Line Items]
Net revenues	11	14	24	23
Corporate and Eliminations [Member]
Disaggregation of Revenue [Line Items]
Net revenues	(25)	(4)	(51)	(11)
Corporate and Eliminations [Member] \| United States [Member]
Disaggregation of Revenue [Line Items]
Net revenues	(25)	(4)	(51)	(11)
Life Safety [Member]
Disaggregation of Revenue [Line Items]
Net revenues	428	322	1,199	963
Life Safety [Member] \| Safety Services [Member]
Disaggregation of Revenue [Line Items]
Net revenues	428	322	1,199	963
Heating, Ventilation and Air Conditioning ("HVAC") [Member]
Disaggregation of Revenue [Line Items]
Net revenues	105	82	312	236
Heating, Ventilation and Air Conditioning ("HVAC") [Member] \| Safety Services [Member]
Disaggregation of Revenue [Line Items]
Net revenues	105	82	312	236
Infrastructure/Utility [Member]
Disaggregation of Revenue [Line Items]
Net revenues	220	230	561	615
Infrastructure/Utility [Member] \| Specialty Services [Member]
Disaggregation of Revenue [Line Items]
Net revenues	220	230	561	615
Fabrication [Member]
Disaggregation of Revenue [Line Items]
Net revenues	45	58	186	129
Fabrication [Member] \| Specialty Services [Member]
Disaggregation of Revenue [Line Items]
Net revenues	45	58	186	129
Specialty Contracting [Member]
Disaggregation of Revenue [Line Items]
Net revenues	171	112	425	305
Specialty Contracting [Member] \| Specialty Services [Member]
Disaggregation of Revenue [Line Items]
Net revenues	171	112	425	305
Transmission [Member]
Disaggregation of Revenue [Line Items]
Net revenues	68	127	141	336
Transmission [Member] \| Industrial Services [Member]
Disaggregation of Revenue [Line Items]
Net revenues	68	127	141	336
Civil [Member]
Disaggregation of Revenue [Line Items]
Net revenues	35	25	55	50
Civil [Member] \| Industrial Services [Member]
Disaggregation of Revenue [Line Items]
Net revenues	35	25	55	50
Inspection [Member]
Disaggregation of Revenue [Line Items]
Net revenues		6		82
Inspection [Member] \| Industrial Services [Member]
Disaggregation of Revenue [Line Items]
Net revenues		6		82
Corporate and Eliminations [Member]
Disaggregation of Revenue [Line Items]
Net revenues	(25)	(4)	(51)	(11)
Corporate and Eliminations [Member] \| Corporate and Eliminations [Member]
Disaggregation of Revenue [Line Items]
Net revenues	$ (25)	$ (4)	$ (51)	$ (11)