Estimated Fair Values of Aggregate Assets and Liabilities Acquired (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash	$ 61,786	$ 5,170	$ 1,000
Other current assets	71,824	5,835	2,558
Fixed assets	4,937	1,075	891
Goodwill	390,640	128,344	116,393
Purchased customer accounts	137,946	73,868	65,476
Non-compete agreements	452	506	460
Other assets	1	24	5
Total assets acquired	667,586	214,822	186,783
Other current liabilities	(110,188)	(11,133)	(2,298)
Deferred income taxes, net	(26,488)	(1,455)
Other liabilities		(3,071)
Total liabilities assumed	(136,676)	(15,659)	(2,298)
Net assets acquired	530,910	199,163	184,485
Arrowhead General Insurance Agency Superholding Corporation
Cash	61,786
Other current assets	69,051
Fixed assets	4,629
Goodwill	321,128
Purchased customer accounts	99,675
Non-compete agreements	100
Other assets	1
Total assets acquired	556,370
Other current liabilities	(107,579)
Deferred income taxes, net	(26,488)
Total liabilities assumed	(134,067)
Net assets acquired	422,303
Insurcorp & GGM Investments LLC
Other current assets	180
Fixed assets	25
Goodwill	14,745
Purchased customer accounts	6,490
Non-compete agreements	22
Total assets acquired	21,462
Other current liabilities	(118)
Total liabilities assumed	(118)
Net assets acquired	21,344
Richard W. Endlar Insurance Agency, Inc.
Other current assets	305
Fixed assets	25
Goodwill	8,044
Purchased customer accounts	5,230
Non-compete agreements	11
Total assets acquired	13,615
Other current liabilities	(192)
Total liabilities assumed	(192)
Net assets acquired	13,423
Texas Security General Insurance Agency Inc.
Other current assets	1,866
Fixed assets	45
Goodwill	10,845
Purchased customer accounts	6,229
Non-compete agreements	14
Total assets acquired	18,999
Other current liabilities	(187)
Total liabilities assumed	(187)
Net assets acquired	18,812
Behnke & Associates, Inc.
Fixed assets	25
Goodwill	6,430
Purchased customer accounts	3,843
Non-compete agreements	41
Total assets acquired	10,339
Net assets acquired	10,339
Rowlands & Barranca Agency Inc.
Fixed assets	30
Goodwill	8,363
Purchased customer accounts	3,367
Non-compete agreements	21
Total assets acquired	11,781
Other current liabilities	(635)
Total liabilities assumed	(635)
Net assets acquired	11,146
Other Acquisitions
Other current assets	422	1,059	1,528
Fixed assets	158	65	180
Goodwill	21,085	18,465	36,119
Purchased customer accounts	13,112	13,746	22,841
Non-compete agreements	243	187	332
Other assets		2
Total assets acquired	35,020	33,524	61,000
Other current liabilities	(1,477)	(867)	(1,212)
Total liabilities assumed	(1,477)	(867)	(1,212)
Net assets acquired	33,543	32,657	59,788
Balcos Insurance, Inc., Et Al
Other current assets		187
Fixed assets		20
Goodwill		6,486
Purchased customer accounts		3,530
Non-compete agreements		42
Total assets acquired		10,265
Other current liabilities		(59)
Total liabilities assumed		(59)
Net assets acquired		10,206
Associated Insurance Service, Inc., Et Al
Other current assets		252
Fixed assets		100
Goodwill		9,055
Purchased customer accounts		4,086
Non-compete agreements		92
Total assets acquired		13,585
Other current liabilities		(10)
Total liabilities assumed		(10)
Net assets acquired		13,575
United Benefit Services Insurance Agency, Et Al
Other current assets		438
Fixed assets		20
Goodwill		10,049
Purchased customer accounts		7,045
Non-compete agreements		45
Other assets		4
Total assets acquired		17,601
Other current liabilities		(728)
Total liabilities assumed		(728)
Net assets acquired		16,873
First Horizon Insurance Group, Inc. et al.
Cash		5,170
Other current assets		1,640
Fixed assets		134
Goodwill		15,254
Purchased customer accounts		8,088
Non-compete agreements		10
Other assets		9
Total assets acquired		30,305
Other current liabilities		(3,790)
Deferred income taxes, net		(1,455)
Total liabilities assumed		(5,245)
Net assets acquired		25,060
Fitzharris Agency, Inc. et al.
Other current assets		77
Fixed assets		60
Goodwill		7,244
Purchased customer accounts		3,351
Non-compete agreements		21
Total assets acquired		10,753
Other current liabilities		(3,706)
Total liabilities assumed		(3,706)
Net assets acquired		7,047
Corporate Benefit Consultants, LLC
Other current assets		227
Fixed assets		6
Goodwill		6,738
Purchased customer accounts		4,046
Non-compete agreements		21
Total assets acquired		11,038
Net assets acquired		11,038
Sitzmann, Morris & Lavis Insurance Agency, Inc. et al.
Other current assets		1,372
Fixed assets		465
Goodwill		31,601
Purchased customer accounts		13,995
Non-compete agreements		42
Other assets		4
Total assets acquired		47,479
Other current liabilities		(791)
Total liabilities assumed		(791)
Net assets acquired		46,688
Snapper Shuler Kenner, Inc. et al.
Other current assets		247
Fixed assets		45
Goodwill		5,818
Purchased customer accounts		2,726
Non-compete agreements		12
Total assets acquired		8,848
Other current liabilities		(37)
Total liabilities assumed		(37)
Net assets acquired		8,811
Industry Consulting Group, Inc.
Other current assets		336
Fixed assets		100
Goodwill		9,564
Purchased customer accounts		7,161
Non-compete agreements		11
Other assets		5
Total assets acquired		17,177
Other current liabilities		(1,096)
Other liabilities		(3,071)
Total liabilities assumed		(4,167)
Net assets acquired		13,010
Colonial Claims Corporation et al.
Fixed assets		60
Goodwill		8,070
Purchased customer accounts		6,094
Non-compete agreements		23
Total assets acquired		14,247
Other current liabilities		(49)
Total liabilities assumed		(49)
Net assets acquired		14,198
DiMartino Associates,Inc
Other current assets			137
Fixed assets			21
Goodwill			6,890
Purchased customer accounts			3,380
Non-compete agreements			21
Total assets acquired			10,449
Net assets acquired			10,449
Stone Insurance Agencies, et al.
Other current assets			516
Fixed assets			70
Goodwill			11,128
Purchased customer accounts			5,172
Non-compete agreements			74
Total assets acquired			16,960
Other current liabilities			(1,011)
Total liabilities assumed			(1,011)
Net assets acquired			15,949
Crowe Paradis Holding Company,et al.
Cash			1,000
Other current assets			118
Fixed assets			500
Goodwill			53,573
Purchased customer accounts			28,440
Non-compete agreements			33
Other assets			1
Total assets acquired			83,665
Net assets acquired			83,665
Thomas R Jones, Inc
Other current assets			259
Fixed assets			120
Goodwill			8,683
Purchased customer accounts			5,643
Other assets			4
Total assets acquired			14,709
Other current liabilities			(75)
Total liabilities assumed			(75)
Net assets acquired			$ 14,634