Commitments, Contingencies and Off-Balance Sheet Arrangements - Additional Information (Detail)	3 Months Ended		6 Months Ended		246 Months Ended
	Jun. 30, 2022 USD ($) ft² Entity LetterOfCredit	Jun. 30, 2021 Entity	Jun. 30, 2022 USD ($) ft² Entity LetterOfCredit Employee	Jun. 30, 2021 Entity	Jun. 30, 2022 USD ($) ft² LetterOfCredit Entity
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Number of square feet | ft²	360,000		360,000		360,000
Number of employees will accommodate at new facility | Employee			2,000
Number of companies acquired | Entity	30	26	50	48	635
Aggregate amount of maximum earnout obligations related to acquisitions			$ 1,753,200,000
Aggregate amount of maximum earnout obligations related to acquisitions, recorded in consolidated balance sheet			848,700,000
Aggregate amount of earnout obligation expected settlement in cash or stock at option	$ 588,300,000		588,300,000		$ 588,300,000
Aggregate amount of earnout obligation expected settlement in cash	260,400,000		260,400,000		260,400,000
Debt	$ 9,400,000		9,400,000		$ 9,400,000
Income tax credits and adjustments			$ 108,000,000.0
Security Deposit [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Number of letters of credit issued | LetterOfCredit	2		2		2
Collateral [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Number of letters of credit issued | LetterOfCredit	1		1		1
Self-Insurance Deductibles [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Number of letters of credit issued | LetterOfCredit	2		2		2
Rent-A-Captive Facility [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Number of letters of credit issued | LetterOfCredit	8		8		8
Errors And Omissions [Member] | Up to $4.5 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claims, amount retained			$ 2,000,000.0
Errors And Omissions [Member] | Up to $10 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claims, amount retained			15,000,000.0
Insurance claim arise during ordinary course of business	$ 15,000,000.0		15,000,000.0		$ 15,000,000.0
Errors And Omissions [Member] | Up to $20.0 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claims, amount retained			20,000,000.0
Errors And Omissions [Member] | Up to $27.0 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claims, amount retained			10,000,000.0
Letter of Credit [Member] | Security Deposit [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Debt	500,000		500,000		500,000
Letter of Credit [Member] | Collateral [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Debt	900,000		900,000		900,000
Letter of Credit [Member] | Self-Insurance Deductibles [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Liabilities recorded on self-insurance	17,600,000		17,600,000		17,600,000
Letter of Credit [Member] | Rent-A-Captive Facility [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Debt	2,500,000		2,500,000		2,500,000
Minimum [Member] | Errors And Omissions [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Actuarial range value	4,100,000		4,100,000		4,100,000
Minimum [Member] | Errors And Omissions [Member] | Up to $4.5 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claim arise during ordinary course of business	15,000,000.0		15,000,000.0		15,000,000.0
Minimum [Member] | Errors And Omissions [Member] | Up to $20.0 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claim arise during ordinary course of business	100,000,000.0		100,000,000.0		100,000,000.0
Minimum [Member] | Errors And Omissions [Member] | Up to $27.0 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claim arise during ordinary course of business	225,000,000.0		225,000,000.0		225,000,000.0
Maximum [Member] | Errors And Omissions [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Actuarial range value	5,700,000		5,700,000		5,700,000
Maximum [Member] | Errors And Omissions [Member] | Up to $4.5 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claim arise during ordinary course of business	100,000,000.0		100,000,000.0		100,000,000.0
Maximum [Member] | Errors And Omissions [Member] | Up to $20.0 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claim arise during ordinary course of business	225,000,000.0		225,000,000.0		225,000,000.0
Maximum [Member] | Errors And Omissions [Member] | Up to $27.0 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claim arise during ordinary course of business	$ 365,000,000.0		$ 365,000,000.0		$ 365,000,000.0
Unconsolidated Investments in Enterprises [Member] | Minimum [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Ownership interest	1.00%		1.00%		1.00%
Unconsolidated Investments in Enterprises [Member] | Maximum [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Ownership interest	50.00%		50.00%		50.00%