Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Cash flows from operating activities:
Net income	$ 225,955	$ 203,918
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred sales commissions	11,799	8,154
Non-cash long-term incentive compensation expense	8,976	6,776
Depreciation and other amortization	23,244	22,849
Non-cash lease expense	29,123	26,426
(Gain) loss on assets held for sale	(650)	2,500
Other, net	7,795	(3,523)
Changes in assets and liabilities:
Decrease in securities, segregated	2,094	467,788
(Increase) decrease in receivables	(17,238)	126,176
(Increase) in deferred sales commissions	(31,697)	(14,120)
(Decrease) in payables	(71,542)	(764,090)
Increase (decrease) in accounts payable and accrued expenses	50,615	(12,365)
Increase in accrued compensation and benefits	34,064	23,277
Cash payments to relieve operating lease liabilities	(7,901)	(26,566)
Net cash provided by (used in) operating activities	353,687	(46,912)
Cash flows from investing activities:
Purchases of furniture, equipment and leasehold improvements	(31,289)	(10,572)
Joint venture equalization payment	303,980	0
Net cash provided by (used in) investing activities	272,691	(10,572)
Cash flows from financing activities:
Repayment of debt, net	(254,316)
Proceeds from debt, net		45,000
Increase in overdrafts payable	45,688	86
Distributions to General Partner and Unitholders	(246,044)	(221,919)
Capital contributions (to) affiliates	(891)	(1,324)
Purchases of AB Holding Units to fund long-term incentive compensation plan awards, net	(5,552)	(18,090)
Other, net	(3,052)	(2,339)
Net cash (used in) financing activities	(556,721)	(200,719)
Effect of exchange rate changes on cash and cash equivalents	(10,156)	10,232
Net increase (decrease) in cash and cash equivalents	59,501	(247,971)
Cash and cash equivalents as of beginning of the period	1,160,889	1,309,017	$ 1,309,017
Cash and cash equivalents as of end of the period	1,220,390	1,061,046	$ 1,160,889
Excluding Company-Sponsored Investment Funds
Adjustments to reconcile net income to net cash provided by operating activities:
Unrealized (gains) on investments	(3,734)	(4,662)
Changes in assets and liabilities:
Decrease in investments	30,595	18,571
(Increase) in other assets	(52,798)	(102,965)
Company-Sponsored Investment Funds
Adjustments to reconcile net income to net cash provided by operating activities:
Unrealized (gains) on investments	(7,481)	(16,162)
Changes in assets and liabilities:
Decrease in investments	106,527	(10,641)
Increase in other assets and liabilities of consolidated company-sponsored investment funds, net	15,941	1,747
Cash flows from financing activities:
(Redemptions) of non-controlling interest in consolidated company-sponsored investment funds, net	$ (92,554)	$ (2,133)