Schedule I - Condensed Statements of Financial Condition (Parent Company Only) (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
ASSETS
Cash and cash equivalents	$ 1,389,876	$ 1,231,593	$ 1,246,537
Other assets	307,332	257,199
Total Assets	5,971,861	5,639,581	4,997,241
Liabilities:
Other liabilities	524,538	534,268
Total Liabilities	4,972,428	4,958,007
Commitments and contingencies
Common stock:
Class A, par value $.01 per share (500,000,000 shares authorized; 112,766,091 shares issued at December 31, 2020 and 2019, including shares held by subsidiaries as indicated below)	1,128	1,128
Additional paid-in-capital	135,439	41,020
Retained earnings	1,295,386	1,193,570
Accumulated other comprehensive loss, net of tax	(238,368)	(293,648)
Stockholders' equity subtotal before common stock held by subsidiaries and Noncontrolling interests, total	1,193,585	942,070
Class A common stock held by subsidiaries, at cost (7,728,387 and 8,513,493 shares at December 31, 2020 and 2019, respectively)	(281,813)	(332,079)
Total Lazard Ltd Stockholders’ Equity	911,772	609,991
Total Liabilities and Stockholders’ Equity	5,971,861	5,639,581
Series A Preferred Stock [Member]
Preferred stock:
Preferred stock
Series B Preferred Stock [Member]
Preferred stock:
Preferred stock
Parent Company [Member]
ASSETS
Cash and cash equivalents	453	2,734	$ 4,136	$ 3,921
Investments in subsidiaries, equity method	(931,614)	(1,259,668)
Due from subsidiaries	1,850,887	1,872,940
Other assets	29	8
Total Assets	919,755	616,014
Liabilities:
Due to subsidiaries	7,829	5,866
Other liabilities	154	157
Total Liabilities	7,983	6,023
Commitments and contingencies
Common stock:
Class A, par value $.01 per share (500,000,000 shares authorized; 112,766,091 shares issued at December 31, 2020 and 2019, including shares held by subsidiaries as indicated below)	1,128	1,128
Additional paid-in-capital	135,439	41,020
Retained earnings	1,295,386	1,193,570
Accumulated other comprehensive loss, net of tax	(238,368)	(293,648)
Stockholders' equity subtotal before common stock held by subsidiaries and Noncontrolling interests, total	1,193,585	942,070
Class A common stock held by subsidiaries, at cost (7,728,387 and 8,513,493 shares at December 31, 2020 and 2019, respectively)	(281,813)	(332,079)
Total Lazard Ltd Stockholders’ Equity	911,772	609,991
Total Liabilities and Stockholders’ Equity	919,755	616,014
Parent Company [Member] | Series A Preferred Stock [Member]
Preferred stock:
Preferred stock
Parent Company [Member] | Series B Preferred Stock [Member]
Preferred stock:
Preferred stock