Accumulated Other Comprehensive Income (Loss), Net of Tax (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Accumulated Other Comprehensive Income Loss [Line Items]
Currency translation adjustments	$ 16,071	$ 3,719
Interest rate hedge	(2,766)	(3,557)
Employee benefit plans	(98,140)	(92,637)
Total AOCI	(84,835)	(92,475)
Less amount attributable to noncontrolling interests	(3,427)	(4,111)
Total Lazard Ltd AOCI	$ (81,408)	$ (88,364)