Stockholders' Equity - Additional Information (Detail) - USD ($)		3 Months Ended		9 Months Ended
	Oct. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Oct. 31, 2019	Dec. 31, 2018
Schedule Of Stockholders Equity [Line Items]
Aggregate value of all shares repurchased		$ 78,569,000	$ 82,796,000	$ 430,281,000	$ 306,591,000
Share repurchase remaining authorization		$ 165,231,000		$ 165,231,000
Share repurchase authorization expiration date				Dec. 31, 2020
Preferred stock, shares authorized		15,000,000		15,000,000			15,000,000
Preferred stock, par value		$ 0.01		$ 0.01			$ 0.01
Dividend declared per share of common stock		$ 0.47	$ 0.44	$ 1.88	$ 2.59
Subsequent Event [Member] | Quarterly Dividend [Member]
Schedule Of Stockholders Equity [Line Items]
Dividend declared per share of common stock	$ 0.47
Dividend payable date	Nov. 22, 2019
Dividend date of record	Nov. 11, 2019
Dividend declare date	Oct. 30, 2019
30 October, 2019 [Member] | Subsequent Event [Member]
Schedule Of Stockholders Equity [Line Items]
Share repurchase remaining authorization	$ 437,000,000
Share repurchase authorization expiration date	Dec. 31, 2021
Share Repurchase Authorization	$ 300,000,000
Class A Common Stock [Member] | Executive Officers [Member]
Schedule Of Stockholders Equity [Line Items]
Aggregate value of all shares repurchased				$ 14,600,000	$ 16,400,000
Class A Common Stock [Member] | Lazard Group LLC [Member] | Subsequent Event [Member]
Schedule Of Stockholders Equity [Line Items]
Number of shares distributed to the parent						17,000,000
Series A Preferred Stock [Member]
Schedule Of Stockholders Equity [Line Items]
Preferred stock, shares outstanding		0		0			0
Series B Preferred Stock [Member]
Schedule Of Stockholders Equity [Line Items]
Preferred stock, shares outstanding		0		0			0