Segment Information - Summarized Financial Information Reportable Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Total revenues	$ 404,298us-gaap_Revenues	$ 363,594us-gaap_Revenues
Investment income	220us-gaap_InvestmentIncomeNonoperating	103us-gaap_InvestmentIncomeNonoperating
Amortization	21,625us-gaap_AdjustmentForAmortization	17,876us-gaap_AdjustmentForAmortization
Depreciation	5,183us-gaap_Depreciation	4,640us-gaap_Depreciation
Interest expense	9,851us-gaap_InterestExpense	4,072us-gaap_InterestExpense
Income before income taxes	93,778	86,837
Total assets	4,838,942us-gaap_Assets	3,674,289us-gaap_Assets	4,956,458us-gaap_Assets
Capital expenditures	3,727	4,727
Operating Segments \| Retail
Segment Reporting Information [Line Items]
Total revenues	218,344	205,470
Investment income	22	16
Amortization	10,934	10,269
Depreciation	1,642	1,593
Interest expense	10,158	10,745
Income before income taxes	47,009	41,217
Total assets	3,305,917	3,057,253
Capital expenditures	1,424	2,116
Operating Segments \| National Programs
Segment Reporting Information [Line Items]
Total revenues	99,555	76,675
Investment income	45	5
Amortization	7,235	3,864
Depreciation	1,766	1,489
Interest expense	14,955	5,442
Income before income taxes	9,476	16,944
Total assets	2,407,695	1,376,590
Capital expenditures	1,489	1,889
Operating Segments \| Wholesale Brokerage
Segment Reporting Information [Line Items]
Total revenues	51,828	50,001
Investment income	72	4
Amortization	2,423	2,676
Depreciation	563	619
Interest expense	229	386
Income before income taxes	14,484	10,747
Total assets	858,149	877,555
Capital expenditures	451	287
Operating Segments \| Services
Segment Reporting Information [Line Items]
Total revenues	34,788	31,642
Investment income	0	2
Amortization	1,023	1,057
Depreciation	530	463
Interest expense	1,599	1,970
Income before income taxes	4,502	2,769
Total assets	300,155	276,219
Capital expenditures	240	291
Other
Segment Reporting Information [Line Items]
Total revenues	(217)	(194)
Investment income	81	76
Amortization	10	10
Depreciation	682	476
Interest expense	(17,090)	(14,471)
Income before income taxes	18,307	15,160
Total assets	(2,032,974)	(1,913,328)
Capital expenditures	$ 123	$ 144

The aggregate amount of recurring noncash expense charged against earnings in the period to allocate the cost of assets over their estimated remaining economic lives.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

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- Definition

Amount of the cost of borrowed funds accounted for as interest expense.

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-Topic 835

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The aggregate amount of income from investments (for example, dividends) not considered a component of the entity's core operations.

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The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.

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-Glossary Investing Activities

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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