Business Combinations - Estimated Fair Values of Aggregate Assets and Liabilities Acquired (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Fair Value Of Assets And Liabilities Statement [Line Items]
Business Acquisitions Purchase Price Allocation Current Assets Cash And Cash Equivalents	$ 2,094,000
Payments to Acquire Businesses, Gross	42,697,000	$ 36,200,000
Recorded Earn-Out Payable	606,000
Other current assets	1,379,000
Fixed assets	349,000
Goodwill	28,952,000
Purchased customer accounts	16,779,000
Non-compete agreements	134,000
Total assets acquired	49,687,000
Other current liabilities	(2,362,000)
Deferred Tax Liabilities, Net	(3,230,000)
Total liabilities assumed	(5,592,000)
Net assets acquired	44,095,000
Maximum Potential Earn- Out Payable	5,474,000
SSAD [Member]
Fair Value Of Assets And Liabilities Statement [Line Items]
Business Acquisitions Purchase Price Allocation Current Assets Cash And Cash Equivalents	2,094,000
Other current assets	1,042,000
Fixed assets	307,000
Goodwill	22,294,000
Purchased customer accounts	13,069,000
Non-compete agreements	72,000
Total assets acquired	38,878,000
Other current liabilities	(1,686,000)
Deferred Tax Liabilities, Net	(3,230,000)
Total liabilities assumed	(4,916,000)
Net assets acquired	33,962,000
Other Acquisitions [Member]
Fair Value Of Assets And Liabilities Statement [Line Items]
Business Acquisitions Purchase Price Allocation Current Assets Cash And Cash Equivalents	0
Other current assets	337,000
Fixed assets	42,000
Goodwill	6,658,000
Purchased customer accounts	3,710,000
Non-compete agreements	62,000
Total assets acquired	10,809,000
Other current liabilities	(676,000)
Deferred Tax Liabilities, Net	0
Total liabilities assumed	(676,000)
Net assets acquired	10,133,000
Wholesale Brokerage
Fair Value Of Assets And Liabilities Statement [Line Items]
Goodwill	$ 24,000