Revenue - Additional Information (Detail) $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($) Customer	Dec. 31, 2019 USD ($) Customer	Dec. 31, 2018 USD ($) Customer
Disaggregation Of Revenue [Line Items]
Receivable from clients balance \| $	$ 563	$ 470	$ 377
Number of customers \| Customer	1	1	1
Sales Revenue Net [Member] \| Customer [Member]
Disaggregation Of Revenue [Line Items]
Concentration Risk, Percentage	13.00%	14.00%	14.00%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9054-108599

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 275
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-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration