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Commitments, Contingencies and Off-Balance Sheet Arrangements - Additional Information (Detail) | 3 Months Ended | 183 Months Ended
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Mar. 31, 2017 USD ($) ft² Entity Employees LetterOfCredit | Mar. 31, 2016 Entity | Mar. 31, 2017 USD ($) ft² 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 | 40 | 32 | 432
Aggregate amount of maximum earnout obligations related to acquisitions | $ 565,300,000 |  |
Aggregate amount of maximum earnout obligations related to acquisitions, recorded in consolidated balance sheet | $ 268,300,000 |  |
Tax Increment Financing [Member] |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |
Property tax credit expect to receive period | 15 years |  |
Letter of Credit [Member] |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |
Debt | $ 5,000,000 |  | $ 5,000,000
Number of letters of credit issued | LetterOfCredit | 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 |  |
Letter of Credit [Member] | Self-Insurance Deductibles [Member] |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |
Liabilities recorded on self-insurance | $ 9,300,000 |  | 9,300,000
Debt | $ 12,300,000 |  | 12,300,000
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 |  |
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%
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
Outstanding Purchase Obligations Related to New Corporate Headquarters Building [Member] |  |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |
Contractual Obligations, Payments Due by Period, Total | $ 7,200,000 |  | $ 7,200,000

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