Segment Reporting (Detail) (USD $)	3 Months Ended								6 Months Ended	12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2013	Dec. 31, 2014 segment	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting
Number of operating segments										4
Segment reporting
Total revenues	$ 148,966,000	$ 134,773,000	$ 138,466,000	$ 137,609,000	$ 131,900,000	$ 127,558,000	$ 139,293,000	$ 132,050,000		$ 559,814,000	$ 530,801,000	$ 504,436,000
Income (loss) before income tax expense (benefit)	17,801,000	12,078,000	16,688,000	18,420,000	10,643,000	10,690,000	10,770,000	10,952,000		64,987,000	43,055,000	(270,455,000)
Identifiable assets	1,350,849,000				1,539,472,000					1,350,849,000	1,539,472,000	1,492,976,000
Capital purchases										13,798,000	33,549,000	33,424,000
Depreciation and amortization										49,384,000	53,606,000	56,493,000
Share-based compensation										18,874,000	20,861,000	15,628,000
Facility closing expense											1,600,000
Restructuring charges							(75,000)				(75,000)	9,499,000
Duplicate rent charges									2,600,000		2,600,000	1,400,000
Non-operating charge , which included a reserve for the remaining lease obligation for the previous midtown Manhattan headquarters							3,900,000
Impairment charges on goodwill included in loss before income tax benefits										(13,801,000)	101,000	274,285,000
Carrying value of goodwill	12,803,000									12,803,000
Long-lived Assets	146,724,000				135,947,000					146,724,000	135,947,000	135,465,000
Restructuring accruals recorded in 2012 and 2011
Segment reporting
Reduction in previously recorded restructuring accruals											1,600,000
U.S. Operations
Segment reporting
Total revenues										306,933,000	318,036,000	321,379,000
Income (loss) before income tax expense (benefit)										15,779,000	15,687,000	(248,101,000)
Identifiable assets	929,062,000				1,183,986,000					929,062,000	1,183,986,000	1,238,822,000
Capital purchases										10,645,000	28,367,000	29,159,000
Depreciation and amortization										38,659,000	43,017,000	44,585,000
Share-based compensation										11,209,000	10,932,000	10,449,000
Impairment charges on goodwill included in loss before income tax benefits												245,100,000
Long-lived Assets	107,746,000				116,812,000					107,746,000	116,812,000	115,726,000
Canadian Operations
Segment reporting
Total revenues										78,093,000	74,994,000	76,913,000
Income (loss) before income tax expense (benefit)										16,729,000	11,441,000	10,397,000
Identifiable assets	105,898,000				88,503,000					105,898,000	88,503,000	99,625,000
Capital purchases										1,656,000	1,188,000	2,575,000
Depreciation and amortization										3,153,000	3,437,000	3,711,000
Share-based compensation										3,795,000	6,852,000	2,543,000
Long-lived Assets	7,070,000				5,676,000					7,070,000	5,676,000	7,174,000
European Operations
Segment reporting
Total revenues										127,563,000	91,792,000	67,266,000
Income (loss) before income tax expense (benefit)										34,004,000	18,106,000	(24,350,000)
Identifiable assets	249,702,000				202,015,000					249,702,000	202,015,000	108,675,000
Capital purchases										1,114,000	3,323,000	923,000
Depreciation and amortization										6,422,000	6,012,000	6,918,000
Share-based compensation										2,891,000	2,223,000	2,091,000
Impairment charges on goodwill included in loss before income tax benefits												28,500,000
Long-lived Assets	29,531,000				11,413,000					29,531,000	11,413,000	10,260,000
Asia Pacific Operations
Segment reporting
Total revenues										47,225,000	45,979,000	38,878,000
Income (loss) before income tax expense (benefit)										(1,525,000)	(2,179,000)	(8,401,000)
Identifiable assets	66,187,000				64,968,000					66,187,000	64,968,000	45,854,000
Capital purchases										383,000	671,000	767,000
Depreciation and amortization										1,150,000	1,140,000	1,279,000
Share-based compensation										979,000	854,000	545,000
Impairment charges on goodwill included in loss before income tax benefits												700,000
Long-lived Assets	$ 2,377,000				$ 2,046,000					$ 2,377,000	$ 2,046,000	$ 2,305,000