Goodwill and Intangibles - Summary of Changes In Carrying Amounts of Goodwill By Reportable Segments (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
Mar. 31, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019
Goodwill [LineItems]
Beginning Balance	$ 980	$ 320	$ 980	$ 320
Acquisitions		4	225	981
Impairments	(193)	(12)	(193)
Transfers and other				(1)
Measurement period adjustments and other			70
Ending Balance		312	1,082	980
Safety Services [Member]
Goodwill [LineItems]
Beginning Balance	639	170	639	170
Acquisitions			223	639
Impairments	(83)		(83)
Measurement period adjustments and other			127
Ending Balance		170	906	639
Specialty Services [Member]
Goodwill [LineItems]
Beginning Balance	290	125	290	125
Acquisitions		4	2	290
Impairments	(52)	(12)	(52)
Measurement period adjustments and other			(68)
Ending Balance		117	172	290
Industrial Services [Member]
Goodwill [LineItems]
Beginning Balance	51	25	51	25
Acquisitions				52
Impairments	$ (58)		(58)
Transfers and other				(1)
Measurement period adjustments and other			11
Ending Balance		$ 25	$ 4	$ 51

Goodwill impairment loss at business with ongoing operations.

No definition available.

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- Definition

Goodwill, transfers and other.

+ References

No definition available.

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- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(10)(1))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

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-Topic 350
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- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

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-Topic 350
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Amount of increase (decrease) from foreign currency translation adjustments and purchase accounting adjustments of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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