Stockholders' Equity - Accumulated Other Comprehensive Income (Loss), Net of Tax (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ 1,293,813	$ 1,367,306
Other comprehensive income (loss) before reclassifications	16,437	11,598
Adjustments for items reclassified to earnings, net of tax	1,086	1,186
OTHER COMPREHENSIVE INCOME, NET OF TAX	17,523	12,784
Balance	1,213,187	1,222,748
Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(155,204)	(97,284)
Other comprehensive income (loss) before reclassifications	16,932	11,739
OTHER COMPREHENSIVE INCOME, NET OF TAX	16,932	11,739
Balance	(138,272)	(85,545)
Employee Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(159,020)	(137,073)
Other comprehensive income (loss) before reclassifications	(495)	(141)
Adjustments for items reclassified to earnings, net of tax	1,086	1,186
OTHER COMPREHENSIVE INCOME, NET OF TAX	591	1,045
Balance	(158,429)	(136,028)
Total AOCI [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(314,224)	(234,357)
Balance	(296,701)	(221,573)
AOCI Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(2)	(1)
Balance	(2)	(1)
Total Lazard LTD AOCI [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(314,222)	(234,356)
Other comprehensive income (loss) before reclassifications	16,437	11,598
Adjustments for items reclassified to earnings, net of tax	1,086	1,186
OTHER COMPREHENSIVE INCOME, NET OF TAX	17,523	12,784
Balance	$ (296,699)	$ (221,572)