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Commitments, Contingencies and Off-Balance Sheet Arrangements - Additional Information (Detail) | 3 Months Ended | 24 Months Ended | 195 Months Ended
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Mar. 31, 2018 USD ($) ft² LetterOfCredit Entity Employees | Mar. 31, 2017 USD ($) LetterOfCredit Entity | Dec. 31, 2017 USD ($) | Mar. 31, 2018 USD ($) 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 |  |  |
Acquired property through lease area, sqft | ft² | 306,000 |  |  |
Acquired property through lease percentage of building | 60.00% |  |  |
Operating lease commitment, expiration date | Feb. 28, 2018 |  |  |
Number of companies acquired | Entity | 39 | 40 |  | 466
Aggregate amount of maximum earnout obligations related to acquisitions | $ 571,000,000 |  |  |
Aggregate amount of maximum earnout obligations related to acquisitions, recorded in consolidated balance sheet | $ 270,900,000 |  |  |
Tax Increment Financing [Member] |  |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |  |
Property tax credit expect to receive period | 15 years |  |  |
Economic development for growing economy tax credit | $ 11,000,000 |  |  | $ 11,000,000
Letter of Credit [Member] |  |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |  |
Liabilities recorded on self-insurance | $ 700,000 |  |  | $ 700,000
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 |  | $ 9,700,000 |  |
Liabilities recorded on self-insurance |  | $ 13,600,000 |  |
Number of letters of credit issued | LetterOfCredit |  | 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%
Minimum [Member] | Tax Increment Financing [Member] |  |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |  |
Property tax credit expect to receive | $ 60,000,000 |  |  | $ 60,000,000
Maximum [Member] |  |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |  |
Ownership interest | 50.00% |  |  | 50.00%
Micro-captive operations, net earnings |  |  | $ 3,500,000 |
Micro-captive operations, EBITDAC |  |  | $ 5,000,000 |
Maximum [Member] | Tax Increment Financing [Member] |  |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |  |
Property tax credit expect to receive | $ 80,000,000 |  |  | $ 80,000,000

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