Summarized Financial Information Reportable Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Total revenues	$ 325,792	$ 290,916	$ 660,804	$ 593,402
Investment income	239	187	425	322
Amortization	16,121	15,881	32,282	31,494
Depreciation	4,263	3,784	8,430	7,425
Interest expense	3,997	4,000	7,981	8,087
Income before income taxes	86,221	71,145	185,712	153,935
Total assets	3,326,320	3,097,291	3,326,320	3,097,291	3,128,058
Capital expenditures	4,176	6,772	7,123	12,677
Operating Segments [Member] | Retail [Member]
Segment Reporting Information [Line Items]
Total revenues	171,819	162,019	346,387	329,223
Investment income	23	27	46	52
Amortization	8,789	8,652	17,600	17,179
Depreciation	1,371	1,294	2,742	2,552
Interest expense	5,649	6,704	11,849	13,638
Income before income taxes	44,482	33,886	90,693	76,086
Total assets	2,501,084	2,229,198	2,501,084	2,229,198
Capital expenditures	1,488	1,574	2,823	2,635
Operating Segments [Member] | National Programs [Member]
Segment Reporting Information [Line Items]
Total revenues	68,354	52,966	137,294	117,573
Investment income	5	11	10	11
Amortization	3,511	3,278	7,030	6,454
Depreciation	1,326	1,136	2,574	2,278
Interest expense	5,590	4,351	11,284	11,003
Income before income taxes	11,226	9,238	25,238	25,195
Total assets	1,224,175	1,149,268	1,224,175	1,149,268
Capital expenditures	1,420	3,434	2,312	5,850
Operating Segments [Member] | Wholesale Brokerage [Member]
Segment Reporting Information [Line Items]
Total revenues	54,823	47,483	103,520	90,787
Investment income	4	5	9	11
Amortization	2,887	2,786	5,784	5,573
Depreciation	716	661	1,423	1,317
Interest expense	723	895	1,478	2,121
Income before income taxes	15,760	11,195	26,122	20,072
Total assets	925,901	795,134	925,901	795,134
Capital expenditures	561	712	1,097	1,886
Operating Segments [Member] | Services [Member]
Segment Reporting Information [Line Items]
Total revenues	30,403	27,660	73,050	53,490
Investment income			1
Amortization	925	1,156	1,849	2,269
Depreciation	401	304	798	529
Interest expense	1,883	4,481	3,804	6,001
Income before income taxes	2,589	2,618	16,542	5,605
Total assets	246,235	268,629	246,235	268,629
Capital expenditures	379	444	498	805
Operating Segments [Member] | Other [Member]
Segment Reporting Information [Line Items]
Total revenues	393	788	553	2,329
Investment income	207	144	359	248
Amortization	9	9	19	19
Depreciation	449	389	893	749
Interest expense	(9,848)	(12,431)	(20,434)	(24,676)
Income before income taxes	12,164	14,208	27,117	26,977
Total assets	(1,571,075)	(1,344,938)	(1,571,075)	(1,344,938)
Capital expenditures	$ 328	$ 608	$ 393	$ 1,501