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Commitments, Contingencies and Off-Balance Sheet Arrangements - Additional Information (Detail) | 12 Months Ended | 216 Months Ended
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Dec. 31, 2019 USD ($) ft² Companies Employees LetterOfCredit Entity | Dec. 31, 2018 USD ($) Entity | Dec. 31, 2017 USD ($) Entity | Dec. 31, 2019 USD ($) ft² LetterOfCredit Entity
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |  |
Number of square feet | ft² | 360,000 |  |  | 360,000
Number of employees will accommodate at new facility | Employees | 2,000 |  |  |
Lease abandonment charges |  |  | $ 13,200,000 |
Total rent expense | $ 148,100,000 | $ 140,000,000.0 | $ 137,700,000 |
Number of companies acquired | Entity | 116 | 112 | 108 | 556
Aggregate amount of maximum earnout obligations related to acquisitions | $ 982,900,000 | $ 558,100,000 |  |
Aggregate amount of maximum earnout obligations related to acquisitions, recorded in consolidated balance sheet | $ 565,000,000.0 | $ 258,800,000 |  |
Ownership interest | 50.00% |  |  | 50.00%
Debt | $ 18,500,000 |  |  | $ 18,500,000
Liabilities recorded on self-insurance | 16,500,000 |  |  | 16,500,000
Income tax credits and adjustments | 108,000,000.0 |  |  |
Errors And Omissions [Member] |  |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |  |
Insurance claims, amount retained | 5,000,000.0 |  |  |
Amount of losses in excess of retained amounts | 350,000,000.0 |  |  | 350,000,000.0
Tax Increment Financing [Member] |  |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |  |
Economic development for growing economy tax credit | 18,100,000 |  |  | 18,100,000
Letter of Credit [Member] |  |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |  |
Debt | $ 900,000 |  |  | $ 900,000
Number of letters of credit issued | LetterOfCredit | 1 |  |  | 1
Letter of Credit [Member] | Security Deposit [Member] |  |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |  |
Debt | $ 500,000 |  |  | $ 500,000
Number of letters of credit issued | LetterOfCredit | 1 |  |  | 1
Letter of Credit [Member] | Self-Insurance Deductibles [Member] |  |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |  |
Debt | $ 9,400,000 |  |  | $ 9,400,000
Liabilities recorded on self-insurance | $ 16,500,000 |  |  | $ 16,500,000
Number of letters of credit issued | LetterOfCredit | 2 |  |  | 2
Letter of Credit [Member] | Rent-A-Captive Facility [Member] |  |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |  |
Debt | $ 6,300,000 |  |  | $ 6,300,000
Number of letters of credit issued | LetterOfCredit | 7 |  |  | 7
Minimum [Member] |  |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |  |
Ownership interest | 1.00% |  |  | 1.00%
Number of micro-captive insurance companies organized or managed | Companies | 100 |  |  |
Minimum [Member] | Errors And Omissions [Member] |  |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |  |
Actuarial range value | $ 2,400,000 |  |  | $ 2,400,000
Minimum [Member] | Tax Increment Financing [Member] |  |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |  |
Property tax credit expect to receive | $ 60,000,000.0 |  |  | $ 60,000,000.0
Maximum [Member] |  |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |  |
Ownership interest | 50.00% |  |  | 50.00%
Micro-captive operations, net earnings | $ 2,900,000 |  |  |
Micro-captive operations, EBITDAC | 4,500,000 |  |  |
Maximum [Member] | Errors And Omissions [Member] |  |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |  |
Actuarial range value | 4,200,000 |  |  | $ 4,200,000
Maximum [Member] | Tax Increment Financing [Member] |  |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |  |
Property tax credit expect to receive | $ 90,000,000.0 |  |  | $ 90,000,000.0

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