Summarized Financial Information Reportable Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Total revenues	$ 359,310	$ 303,800	$ 1,020,114	$ 897,202
Investment income	85	239	510	561
Amortization	17,858	15,956	50,140	47,450
Depreciation	4,466	3,958	12,896	11,383
Interest expense	4,135	4,006	12,116	12,093
Income before income taxes	95,455	81,649	281,167	235,584
Total assets	3,554,788	3,134,729	3,554,788	3,134,729	3,128,058
Capital expenditures	4,330	6,238	11,453	18,915
Operating Segments [Member] | Retail [Member]
Segment Reporting Information [Line Items]
Total revenues	192,845	157,824	539,232	487,047
Investment income	19	32	65	84
Amortization	10,258	8,686	27,858	25,865
Depreciation	1,536	1,296	4,278	3,848
Interest expense	11,127	6,635	22,976	20,273
Income before income taxes	37,441	34,925	128,134	111,011
Total assets	2,918,824	2,250,245	2,918,824	2,250,245
Capital expenditures	1,696	1,376	4,519	4,011
Operating Segments [Member] | National Programs [Member]
Segment Reporting Information [Line Items]
Total revenues	77,816	66,847	215,110	184,420
Investment income	4	5	14	16
Amortization	3,781	3,286	10,811	9,740
Depreciation	1,384	1,204	3,958	3,482
Interest expense	6,245	5,737	17,529	16,740
Income before income taxes	17,450	17,989	42,688	43,184
Total assets	1,350,689	1,163,807	1,350,689	1,163,807
Capital expenditures	1,349	1,993	3,661	7,843
Operating Segments [Member] | Wholesale Brokerage [Member]
Segment Reporting Information [Line Items]
Total revenues	59,324	50,464	162,844	141,251
Investment income	7	6	16	17
Amortization	2,884	2,819	8,668	8,392
Depreciation	684	704	2,107	2,021
Interest expense	642	922	2,120	3,043
Income before income taxes	20,152	15,688	46,274	35,760
Total assets	915,515	784,736	915,515	784,736
Capital expenditures	277	471	1,374	2,357
Operating Segments [Member] | Services [Member]
Segment Reporting Information [Line Items]
Total revenues	30,020	28,695	103,070	82,185
Investment income			1
Amortization	925	1,155	2,774	3,424
Depreciation	402	351	1,200	880
Interest expense	1,804	2,981	5,608	8,982
Income before income taxes	5,763	2,922	22,305	8,527
Total assets	252,801	273,346	252,801	273,346
Capital expenditures	639	1,470	1,137	2,275
Other [Member]
Segment Reporting Information [Line Items]
Total revenues	(695)	(30)	(142)	2,299
Investment income	55	196	414	444
Amortization	10	10	29	29
Depreciation	460	403	1,353	1,152
Interest expense	(15,683)	(12,269)	(36,117)	(36,945)
Income before income taxes	14,649	10,125	41,766	37,102
Total assets	(1,883,041)	(1,337,405)	(1,883,041)	(1,337,405)
Capital expenditures	$ 369	$ 928	$ 762	$ 2,429