Supplemental Financial Information - Quarterly Results (Unaudited) - Schedule of Quarterly Financial Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended								12 Months Ended
	Dec. 11, 2012	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly Operating Results Unaudited [Line Items]
Net revenue		$ 560,693	$ 428,806	$ 436,910	$ 486,039	$ 451,778	$ 462,419	$ 477,292	$ 438,023	$ 1,912,448	$ 1,829,512	$ 1,905,368
Operating expenses		565,890	382,080	392,377	448,216	466,665	374,681	388,090	364,577	1,788,563	1,594,013	1,661,718
Operating Income (Loss)		(5,197)	46,726	44,533	37,823	(14,887)	87,738	89,202	73,446	123,885	235,499	243,650
Net income (loss)		(4,106)	33,673	34,162	29,056	(8,123)	67,133	71,566	59,983	92,785	190,559	194,423
LESS - NET INCOME ATTRIBUTABLE TO NONCONTROLLING INTERESTS		1,259	372	3,341	3,504	(3,330)	4,434	9,562	4,976	8,476	15,642	19,444
Net income (loss) attributable to Lazard Ltd		$ (5,365)	$ 33,301	$ 30,821	$ 25,552	$ (4,793)	$ 62,699	$ 62,004	$ 55,007	$ 84,309	$ 174,917	$ 174,979
Net income (loss) per share of common stock:
Basic		$ (0.05)	$ 0.29	$ 0.26	$ 0.21	$ (0.04)	$ 0.53	$ 0.52	$ 0.48	$ 0.72	$ 1.48	$ 1.68
Diluted		$ (0.05)	$ 0.26	$ 0.24	$ 0.20	$ (0.04)	$ 0.49	$ 0.48	$ 0.43	$ 0.65	$ 1.36	$ 1.36
DIVIDENDS DECLARED PER SHARE OF COMMON STOCK	$ 0.40	$ 0.60	$ 0.20	$ 0.20	$ 0.16	$ 0.160	$ 0.160	$ 0.160	$ 0.125	$ 1.160	$ 0.605	$ 0.500