Supplemental Financial Information - Quarterly Results - Schedule of Quarterly Financial Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 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	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Selected Quarterly Financial Information [Abstract]
Net Revenue	$ 633,940	$ 566,211	$ 566,896	$ 533,400	$ 612,690	$ 480,354	$ 490,405	$ 401,903	$ 2,300,447	$ 1,985,352	$ 1,912,448
Operating expenses	434,347	452,499	467,916	426,220	539,536	399,236	449,467	380,306	1,780,982	1,768,545	1,788,563
Operating Income	199,593	113,712	98,980	107,180	73,154	81,118	40,938	21,597	519,465	216,807	123,885
NET INCOME	172,805	89,920	85,909	85,429	52,796	62,748	31,921	17,649	434,063	165,114	92,785
Less - net income (loss) attributable to noncontrolling interests	421	1,061	717	4,587	(421)	2,466	568	2,289	6,786	4,902	8,476
Net income attributable to Lazard Ltd	$ 172,384	$ 88,859	$ 85,192	$ 80,842	$ 53,217	$ 60,282	$ 31,353	$ 15,360	$ 427,277	$ 160,212	$ 84,309
NET INCOME PER SHARE OF COMMON STOCK:
Basic	$ 1.41	$ 0.73	$ 0.69	$ 0.66	$ 0.44	$ 0.49	$ 0.26	$ 0.13	$ 3.49	$ 1.33	$ 0.72
Diluted	$ 1.29	$ 0.67	$ 0.64	$ 0.61	$ 0.40	$ 0.45	$ 0.24	$ 0.12	$ 3.20	$ 1.21	$ 0.65
DIVIDENDS DECLARED PER SHARE OF COMMON STOCK	$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 0.50	$ 0.25	$ 0.25		$ 1.20	$ 1.00	$ 1.16