Business Segment Information - Financial Information Regarding Company's Operations by Geographic Area (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	$ 1,410,485	$ 1,411,370
Total revenues	1,410,485	1,411,370
Net revenues	445,284	446,571
Operating income	128,518	125,271
Identifiable assets at quarter end	3,017,799	3,001,223	2,954,125
Capital expenditures	10,068	17,088
Depreciation and amortization	11,278	9,545
Equity	2,104,621	2,102,034	2,032,570	2,010,069
United States
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	371,719	377,302
Transfers between geographic areas	20,026	22,208
Total revenues	391,745	399,510
Net revenues	177,688	181,475
Operating income	47,353	45,525
Identifiable assets at quarter end	1,502,795	1,590,900
Capital expenditures	5,379	9,759
Depreciation and amortization	6,757	5,622
Equity	1,231,424	1,315,321
Other North America
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	51,729	49,954
Transfers between geographic areas	2,544	2,465
Total revenues	54,273	52,419
Net revenues	23,781	22,242
Operating income	6,612	6,369
Identifiable assets at quarter end	96,555	96,312
Capital expenditures	187	176
Depreciation and amortization	207	187
Equity	62,267	56,341
Latin America
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	19,864	19,269
Transfers between geographic areas	4,876	5,079
Total revenues	24,740	24,348
Net revenues	14,411	14,835
Operating income	4,089	4,762
Identifiable assets at quarter end	53,935	52,214
Capital expenditures	259	255
Depreciation and amortization	241	217
Equity	32,638	31,060
Asia Pacific
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	694,095	688,070
Transfers between geographic areas	10,630	10,972
Total revenues	704,725	699,042
Net revenues	135,507	131,814
Operating income	52,884	47,238
Identifiable assets at quarter end	795,946	708,528
Capital expenditures	2,552	5,287
Depreciation and amortization	1,988	1,624
Equity	568,609	471,498
Europe and Africa
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	202,487	206,271
Transfers between geographic areas	8,880	9,467
Total revenues	211,367	215,738
Net revenues	70,589	71,533
Operating income	11,926	14,247
Identifiable assets at quarter end	406,801	404,839
Capital expenditures	1,198	942
Depreciation and amortization	1,629	1,404
Equity	165,014	164,165
Middle East and India
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	70,591	70,504
Transfers between geographic areas	4,327	4,651
Total revenues	74,918	75,155
Net revenues	23,308	24,672
Operating income	5,654	7,130
Identifiable assets at quarter end	158,569	149,416
Capital expenditures	493	669
Depreciation and amortization	456	491
Equity	79,434	93,282
Eliminations
Segment Reporting Information [Line Items]
Transfers between geographic areas	(51,283)	(54,842)
Total revenues	(51,283)	(54,842)
Identifiable assets at quarter end	3,198	(986)
Equity	$ (34,765)	$ (29,633)