Operating Segments - Summary of Information about 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
Segment Reporting Information [Line Items]
Revenue	$ 69,815	$ 68,773	$ 220,129	$ 217,870
Direct margin	45,179	45,442	144,213	142,946
Selling, marketing, administrative and other expenses	(40,321)	(37,696)	(123,269)	(116,921)
Amortization of intangible assets	(557)	(579)	(1,670)	(1,779)
Reorganization costs		(37)	(1,905)	(1,431)
Other income (expense) and gains (losses) on investments	(53)	1,112	476	1,794
Income before income taxes	4,248	8,242	17,845	24,609
BT [Member]
Segment Reporting Information [Line Items]
Revenue	37,659	37,764	115,327	115,470
Direct margin	24,912	25,966	78,100	78,882
Selling, marketing, administrative and other expenses
Amortization of intangible assets
Reorganization costs
Other income (expense) and gains (losses) on investments
Income before income taxes
M&S [Member]
Segment Reporting Information [Line Items]
Revenue	31,809	30,707	95,690	92,995
Direct margin	20,923	20,203	62,909	60,823
Selling, marketing, administrative and other expenses
Amortization of intangible assets
Reorganization costs
Other income (expense) and gains (losses) on investments
Income before income taxes
Events [Member]
Segment Reporting Information [Line Items]
Revenue	347	302	9,112	9,405
Direct margin	(656)	(727)	3,204	3,241
Selling, marketing, administrative and other expenses
Amortization of intangible assets
Reorganization costs
Other income (expense) and gains (losses) on investments
Income before income taxes