Schedule I - Condensed Statements of Financial Condition (Parent Company Only) (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
ASSETS
Cash and cash equivalents	$ 1,246,537	$ 1,483,836	$ 1,158,785
Other assets	258,634	228,144
Total Assets	4,997,241	4,928,677	4,556,508
Liabilities:
Other liabilities	576,986	573,588
Total Liabilities	4,027,148	3,669,772
Commitments and contingencies
Common stock:
Class A, par value $.01 per share (500,000,000 shares authorized; 129,766,091 shares issued at December 31, 2018 and 2017, including shares held by subsidiaries as indicated below)	1,298	1,298
Additional paid-in-capital	750,692	788,140
Retained earnings	1,195,563	1,080,413
Accumulated other comprehensive loss, net of tax	(273,818)	(232,518)
Stockholders' equity subtotal before common stock held by subsidiaries and Noncontrolling interests, total	1,673,735	1,637,333
Class A common stock held by subsidiaries, at cost (17,574,805 and 10,747,142 shares at December 31, 2018 and 2017, respectively)	(756,884)	(437,530)
Total Lazard Ltd Stockholders’ Equity	916,851	1,199,803
Total Liabilities and Stockholders’ Equity	4,997,241	4,928,677
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	4,136	3,921	$ 3,916	$ 5,904
Investments in subsidiaries, equity method	(1,275,357)	(1,061,259)
Due from subsidiaries	2,191,915	2,259,112
Other assets	19
Total Assets	920,713	1,201,774
Liabilities:
Due to subsidiaries	3,707	1,847
Other liabilities	155	124
Total Liabilities	3,862	1,971
Commitments and contingencies
Common stock:
Class A, par value $.01 per share (500,000,000 shares authorized; 129,766,091 shares issued at December 31, 2018 and 2017, including shares held by subsidiaries as indicated below)	1,298	1,298
Additional paid-in-capital	750,692	788,140
Retained earnings	1,195,563	1,080,413
Accumulated other comprehensive loss, net of tax	(273,818)	(232,518)
Stockholders' equity subtotal before common stock held by subsidiaries and Noncontrolling interests, total	1,673,735	1,637,333
Class A common stock held by subsidiaries, at cost (17,574,805 and 10,747,142 shares at December 31, 2018 and 2017, respectively)	(756,884)	(437,530)
Total Lazard Ltd Stockholders’ Equity	916,851	1,199,803
Total Liabilities and Stockholders’ Equity	920,713	1,201,774
Parent Company [Member] | Series A Preferred Stock [Member]
Preferred stock:
Preferred stock
Parent Company [Member] | Series B Preferred Stock [Member]
Preferred stock:
Preferred stock