Business Segment Information - Financial Information Regarding Company's Operations by Geographic Area (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	$ 1,501,914	$ 1,606,368	$ 1,581,368	$ 1,460,848	$ 1,582,135	$ 1,667,559	$ 1,516,770	$ 1,201,109	$ 6,150,498	$ 5,967,573	$ 4,092,283
Total revenues									6,150,498	5,967,573	4,092,283
Net revenues	476,155	493,846	472,561	453,915	453,362	458,743	418,858	361,823	1,896,477	1,692,786	1,382,786
Operating income									618,327	547,230	385,001
Identifiable assets at year end	2,866,827				2,679,179				2,866,827	2,679,179	2,323,722
Capital expenditures									78,115	42,408	34,700
Depreciation and amortization									36,776	36,900	40,035
Equity	2,010,069				1,748,154				2,010,069	1,748,154	1,561,347	1,383,916
United States
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers									1,540,477	1,348,259	982,103
Transfers between geographic areas									101,738	99,547	75,964
Total revenues									1,642,215	1,447,806	1,058,067
Net revenues									732,299	666,669	547,879
Operating income									210,702	198,393	117,908
Identifiable assets at year end	1,521,657				1,343,098				1,521,657	1,343,098	1,188,111
Capital expenditures									23,219	18,128	24,908
Depreciation and amortization									20,037	20,125	21,010
Equity	1,285,812				1,089,053				1,285,812	1,089,053	965,620
Other North America
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers									189,843	163,750	129,272
Transfers between geographic areas									11,095	10,836	7,344
Total revenues									200,938	174,586	136,616
Net revenues									90,432	77,079	65,331
Operating income									29,209	23,521	20,253
Identifiable assets at year end	86,020				95,298				86,020	95,298	82,166
Capital expenditures									1,122	574	724
Depreciation and amortization									1,038	1,344	1,391
Equity	49,571				46,601				49,571	46,601	40,421
Latin America
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers									82,312	74,327	64,060
Transfers between geographic areas									21,222	16,932	13,520
Total revenues									103,534	91,259	77,580
Net revenues									59,968	50,937	44,182
Operating income									19,151	15,985	12,538
Identifiable assets at year end	48,221				51,326				48,221	51,326	42,478
Capital expenditures									628	1,320	688
Depreciation and amortization									999	880	1,087
Equity	27,346				27,462				27,346	27,462	17,809
Asia Pacific
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers									3,144,641	3,349,960	2,101,323
Transfers between geographic areas									40,012	32,837	26,771
Total revenues									3,184,653	3,382,797	2,128,094
Net revenues									605,151	543,869	413,627
Operating income									258,952	222,944	167,299
Identifiable assets at year end	667,171				612,085				667,171	612,085	493,338
Capital expenditures									25,295	5,743	2,772
Depreciation and amortization									7,243	7,511	8,106
Equity	448,613				371,610				448,613	371,610	341,991
Europe And Africa
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers									891,185	729,022	582,759
Transfers between geographic areas									43,359	40,778	27,699
Total revenues									934,544	769,800	610,458
Net revenues									307,471	264,663	229,432
Operating income									72,248	63,115	43,953
Identifiable assets at year end	401,518				432,019				401,518	432,019	387,494
Capital expenditures									25,856	14,383	3,407
Depreciation and amortization									5,414	4,661	5,968
Equity	145,998				160,428				145,998	160,428	148,592
Middle East And India
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers									302,040	302,255	232,766
Transfers between geographic areas									17,897	16,184	14,602
Total revenues									319,937	318,439	247,368
Net revenues									101,156	89,569	82,335
Operating income									28,065	23,272	23,050
Identifiable assets at year end	141,379				144,043				141,379	144,043	128,690
Capital expenditures									1,995	2,260	2,201
Depreciation and amortization									2,045	2,379	2,473
Equity	85,605				84,456				85,605	84,456	77,566
Eliminations
Segment Reporting Information [Line Items]
Transfers between geographic areas									(235,323)	(217,114)	(165,900)
Total revenues									(235,323)	(217,114)	(165,900)
Identifiable assets at year end	861				1,310				861	1,310	1,445
Equity	$ (32,876)				$ (31,456)				$ (32,876)	$ (31,456)	$ (30,652)