Basis of Presentation and Summary of Significant Accounting Policies - Concentration of Risk (Detail)	12 Months Ended
	Dec. 31, 2021 HoldingCompany Client Supplier	Dec. 31, 2020 HoldingCompany Client Supplier	Dec. 31, 2019 HoldingCompany
Gross Billings
Concentration Risk [Line Items]
Number of holding company | HoldingCompany	2	2	2
Gross Billings | Two Customers | Minimum | Holding Companies
Concentration Risk [Line Items]
Concentration risk, percentage	10.00%	10.00%	10.00%
Gross Billings | Customer One | Holding Companies
Concentration Risk [Line Items]
Concentration risk, percentage	11.00%	11.00%	13.00%
Gross Billings | Customer Two | Holding Companies
Concentration Risk [Line Items]
Concentration risk, percentage	10.00%	11.00%	10.00%
Consolidated Accounts Receivable
Concentration Risk [Line Items]
Number of client | Client	3	4
Consolidated Accounts Receivable | Customer One | Minimum | Clients
Concentration Risk [Line Items]
Concentration risk, percentage	10.00%	10.00%
Consolidated Accounts Receivable | Customer Two | Minimum | Clients
Concentration Risk [Line Items]
Concentration risk, percentage	10.00%	10.00%
Consolidated Accounts Receivable | Customer Three | Minimum | Clients
Concentration Risk [Line Items]
Concentration risk, percentage	10.00%	10.00%
Consolidated Accounts Receivable | Customer Four | Minimum | Clients
Concentration Risk [Line Items]
Concentration risk, percentage		10.00%
Consolidated Accounts Receivable | All Customers | Clients
Concentration Risk [Line Items]
Concentration risk, percentage	41.00%	51.00%
Trade Accounts Payables | Supplier Concentration Risk
Concentration Risk [Line Items]
Number of supplier | Supplier	1	0
Trade Accounts Payables | Supplier Concentration Risk | Maximum | Supplier
Concentration Risk [Line Items]
Concentration risk, percentage	17.00%	10.00%