Stockholders' Equity - Additional Information (Detail) - USD ($)							3 Months Ended								12 Months Ended
	Feb. 01, 2016	Jan. 27, 2016	Dec. 31, 2015	Dec. 31, 2014	Jun. 26, 2014	May. 12, 2014	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Stockholders Equity [Line Items]
Shares repurchased, value															$ 172,772,000	$ 192,657,000	$ 132,477,000
Share repurchase remaining authorization			$ 106,161,000				$ 106,161,000								$ 106,161,000
Share repurchase authorization expiration date															Dec. 31, 2016
Preferred stock, shares authorized			15,000,000	15,000,000			15,000,000				15,000,000				15,000,000	15,000,000
Preferred stock, par value			$ 0.01	$ 0.01			$ 0.01				$ 0.01				$ 0.01	$ 0.01
Dividend declared per share of common stock							$ 0.35	$ 0.35	$ 0.35	$ 1.30	$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 2.35	$ 1.20	$ 1.00
Lazard Ltd [Member]
Schedule Of Stockholders Equity [Line Items]
Shares in exchanges of a like number of common membership interests																710,009	839,658
Natixis S.A. [Member]
Schedule Of Stockholders Equity [Line Items]
Shares repurchased, value					$ 50,340,000
Shares repurchased, shares					1,000,000
Class A Common Stock [Member]
Schedule Of Stockholders Equity [Line Items]
Common stock held by subsidiaries, shares			4,253,381	7,450,745			4,253,381				7,450,745				4,253,381	7,450,745
Conversion of Series A preferred stock into Class A common stock (in shares)			0	0
Class A Common Stock [Member] | Executive Officers [Member]
Schedule Of Stockholders Equity [Line Items]
Shares repurchased, value						$ 2,000,000									$ 17,700,000	$ 4,800,000	$ 4,700,000
Class A Common Stock [Member] | Subsequent Event [Member]
Schedule Of Stockholders Equity [Line Items]
Share repurchase authorization expiration date		Dec. 31, 2017
New share repurchase authorization repurchase amount		$ 200,000,000
Dividend declared per share of common stock	$ 1.20
Special dividend declared per share of common stock	$ 0.35
Dividend payable date	Feb. 26, 2016
Dividend date of record	Feb. 11, 2016
Dividend declare date	Feb. 01, 2016
Series A Preferred Stock [Member]
Schedule Of Stockholders Equity [Line Items]
Preferred stock, shares outstanding			7,921	7,921			7,921				7,921				7,921	7,921
Series B Preferred Stock [Member]
Schedule Of Stockholders Equity [Line Items]
Preferred stock, shares outstanding			0	0			0				0				0	0