Summarized Financial Information Reportable Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]
Total revenues	$ 343,165	$ 359,310	$ 325,792	$ 335,012	$ 302,830	$ 303,800	$ 290,916	$ 302,486	$ 1,363,279	$ 1,200,032	$ 1,013,542
Investment income									638	797	1,267
Amortization									67,932	63,573	54,755
Depreciation									17,485	15,373	12,392
Interest expense									16,440	16,097	14,132
Income before income taxes	76,442	95,455	86,221	99,491	69,227	81,649	71,145	82,790	357,609	304,811	270,521
Total assets	3,649,508				3,128,058				3,649,508	3,128,058	2,607,011
Capital expenditures									16,366	24,028	13,608
Operating Segments [Member] | Retail [Member]
Segment Reporting Information [Line Items]
Total revenues									728,324	644,429	607,199
Investment income									82	108	102
Amortization									38,052	34,639	33,373
Depreciation									5,847	5,181	5,046
Interest expense									34,407	26,641	27,688
Income before income taxes									166,316	145,214	137,807
Total assets	2,992,087				2,420,759				2,992,087	2,420,759	2,155,413
Capital expenditures									6,847	5,732	6,102
Operating Segments [Member] | National Programs [Member]
Segment Reporting Information [Line Items]
Total revenues									292,130	252,943	164,427
Investment income									19	20
Amortization									14,593	13,936	7,770
Depreciation									5,399	4,600	2,937
Interest expense									24,014	25,674	1,381
Income before income taxes									58,379	51,491	60,465
Total assets	1,335,911				1,183,191				1,335,911	1,183,191	680,251
Capital expenditures									4,743	9,633	1,968
Operating Segments [Member] | Wholesale Brokerage [Member]
Segment Reporting Information [Line Items]
Total revenues									209,907	183,565	174,158
Investment income									22	22	34
Amortization									11,550	11,280	11,032
Depreciation									2,794	2,718	2,594
Interest expense									2,565	3,974	7,495
Income before income taxes									53,822	43,355	36,511
Total assets	927,825				837,364				927,825	837,364	712,212
Capital expenditures									1,931	3,383	2,658
Operating Segments [Member] | Services [Member]
Segment Reporting Information [Line Items]
Total revenues									131,489	116,736	65,972
Investment income									1	1	128
Amortization									3,698	3,680	2,541
Depreciation									1,623	1,278	590
Interest expense									7,321	8,602	5,746
Income before income taxes									24,518	16,770	7,729
Total assets	277,652				238,430				277,652	238,430	166,060
Capital expenditures									1,811	2,519	689
Other [Member]
Segment Reporting Information [Line Items]
Total revenues									1,429	2,359	1,786
Investment income									514	646	1,003
Amortization									39	38	39
Depreciation									1,822	1,596	1,225
Interest expense									(51,867)	(48,794)	(28,178)
Income before income taxes									54,574	47,981	28,009
Total assets	(1,883,967)				(1,551,686)				(1,883,967)	(1,551,686)	(1,106,925)
Capital expenditures									$ 1,034	$ 2,761	$ 2,191