Business Combinations - Acquisitions Accounted for Business Combinations (Detail) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016
Business Combination, Separately Recognized Transactions [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	$ 1,973
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	41,178
Cash Paid	26,478	$ 115,300
Other Payable	11,395
Recorded Earn-Out Payable	1,332
Net Assets Acquired	39,205
Maximum Potential Earn- Out Payable	11,605
Other current assets	98
Fixed assets	47
Goodwill	27,580
Purchased customer accounts	12,858
Non-compete agreements	595
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other	1,284
Deferred Tax Liabilities, Net	689
Services [Member]
Business Combination, Separately Recognized Transactions [Line Items]
Goodwill	689
Services
Business Combination, Separately Recognized Transactions [Line Items]
Goodwill	18,807
National Programs
Business Combination, Separately Recognized Transactions [Line Items]
Goodwill	7,314
Wholesale Brokerage
Business Combination, Separately Recognized Transactions [Line Items]
Goodwill	771
Other Acquisitions [Member]
Business Combination, Separately Recognized Transactions [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	1,973
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	41,178
Net Assets Acquired	39,205
Other current assets	98
Fixed assets	47
Goodwill	27,580
Purchased customer accounts	12,858
Non-compete agreements	595
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other	1,284
Deferred Tax Liabilities, Net	689
Other Acquisitions [Member] \| Various
Business Combination, Separately Recognized Transactions [Line Items]
Cash Paid	26,478
Other Payable	11,395
Recorded Earn-Out Payable	1,332
Net Assets Acquired	39,205
Maximum Potential Earn- Out Payable	$ 11,605

Business Acquisition Cost Of Acquired Entity Other Payable

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- Definition

Business Acquisitions Contingent Consideration At Fair Value

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- Definition

Business Acquisitions Purchase Price Allocation Amortizable Intangible Assets

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Business acquisitions purchase price allocation non-compete agreements gross.

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- Definition

For contingent consideration arrangements recognized in connection with a business combination, this element represents an estimate of the high-end of the potential range (undiscounted) of the consideration which may be paid.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
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Amount of assets acquired at the acquisition date.

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Amount of asset related to consideration paid in advance for costs that provide economic benefits in future periods, and amount of other assets that are expected to be realized or consumed within one year or the normal operating cycle, if longer, acquired at the acquisition date.

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Amount of other liabilities due within one year or within the normal operating cycle, if longer, assumed at the acquisition date.

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Amount of liabilities assumed at the acquisition date.

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Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed.

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

The amount of property, plant, and equipment recognized as of the acquisition date.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences without jurisdictional netting.

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-Publisher FASB
-Name Accounting Standards Codification
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Fair value portion of asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

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