Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net income	$ 778,603	$ 575,067
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred sales commissions	24,866	19,582
Non-cash long-term incentive compensation expense	34,725	23,594
Depreciation and other amortization	97,239	107,910
Unrealized losses on investments	5,203	20,593
Other, net	13,799	(1,072)
Changes in assets and liabilities:
Decrease (increase) in securities, segregated	844,939	(774,447)
(Increase) in receivables	(423,059)	(1,555)
Decrease (increase) in investments	24,052	(8,037)
(Increase) in deferred sales commissions	(36,805)	(46,681)
(Increase) decrease in right-of-use assets	(80,667)	1,845
Increase (decrease) in other assets	(182,775)	40,130
(Decrease) increase in payables	(226,164)	982,957
Increase (Decrease) in lease liabilities	4,103	(71,431)
Increase (decrease) in accounts payable and accrued expenses	35,107	(5,988)
Increase in accrued compensation and benefits	462,274	361,251
Net cash provided by operating activities	1,403,244	1,581,504
Cash flows from investing activities:
Purchases of furniture, equipment and leasehold improvements	(52,074)	(12,357)
Acquisition of business, net of cash acquired	(3,793)	(13,552)
Net cash used in investing activities	(55,867)	(25,909)
Cash flows from financing activities:
(Repayment) of debt, net	(285,000)	(260,000)
Increase in overdrafts payable	24,923	2,640
Distributions to General Partner and Unitholders	(797,811)	(630,882)
Subscriptions (redemptions) of non-controlling interest in consolidated company-sponsored investment funds, net	13,239	(264,021)
Capital contributions to affiliates	(1,914)	(865)
Additional investments by AB Holding with proceeds from exercise of compensatory options to buy AB Holding Units	3,402	147
Purchases of AB Holding Units to fund long-term incentive compensation plan awards, net	(121,461)	(53,458)
Other	1,148	1,276
Net cash used in financing activities	(1,163,474)	(1,205,163)
Effect of exchange rate changes on cash and cash equivalents	(15,038)	1,415
Net increase in cash and cash equivalents	168,865	351,847
Cash and cash equivalents as of beginning of the period	1,073,906	691,171
Cash and cash equivalents as of end of the period	1,242,771	1,043,018
Non-cash investing activities:
Fair value of assets acquired (less cash acquired of $2.8 million and $0.6 million, respectively)	13,235	18,389
Fair value of liabilities assumed	1,642	437
Non-cash financing activities:
Payables recorded under contingent payment arrangements	7,800	4,400
Company-sponsored investment funds
Adjustments to reconcile net income to net cash provided by operating activities:
Unrealized losses on investments	3,878	8,254
Changes in assets and liabilities:
Decrease (increase) in investments	22,505	344,574
Increase (decrease) in other assets	$ 1,421	$ 4,958