Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net income	$ 525,195	$ 593,172
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred sales commissions	10,348	17,362
Non-cash long-term incentive compensation expense	36,737	13,051
Depreciation and other amortization	125,729	52,599
Unrealized (gains) losses on investments	(17,386)	(5,226)
Other, net	3,652	585
Changes in assets and liabilities:
Decrease (increase) in segregated cash and securities	211,405	(446,556)
Decrease (increase) in receivables	214,522	(190,660)
Decrease (increase) in investments	407,616	(30,130)
(Increase) in deferred sales commissions	(20,559)	(3,974)
(Increase) in right-of-use assets	(8,336)
(Increase) decrease in other assets	20,361	(121,016)
(Decrease) increase in payables	(733,097)	584,282
Increase in lease liabilities	(83,161)
(Decrease) in accounts payable and accrued expenses	(39,225)	(24,511)
Increase in accrued compensation and benefits	334,900	395,643
Net cash provided by operating activities	806,018	1,114,383
Cash flows from investing activities:
Purchases of furniture, equipment and leasehold improvements	(24,311)	(26,993)
Acquisition of business, net of cash acquired	5,255	0
Net cash used in investing activities	(19,056)	(26,993)
Cash flows from financing activities:
(Repayment) of commercial paper, net	(227,528)	(97,303)
Proceeds (repayment) of bank loans	55,000	(75,000)
(Decrease) in overdrafts payable	(72,878)	(39,025)
Distributions to General Partner and Unitholders	(514,299)	(652,991)
Capital contributions from (to) affiliates	470	(1,344)
Additional investments by AB Holding with proceeds from exercise of compensatory options to buy AB Holding Units	9,642	10,802
Purchases of AB Holding Units to fund long-term incentive compensation plan awards, net	(81,790)	(82,710)
Other	(2,460)	(2,980)
Net cash used in financing activities	(710,166)	(1,459,152)
Effect of exchange rate changes on cash and cash equivalents	(8,090)	(9,139)
Net increase (decrease) in cash and cash equivalents	68,706	(380,901)
Cash and cash equivalents as of beginning of the period	653,324	998,448
Cash and cash equivalents as of end of the period	722,030	617,547
Non-cash investing activities:
Fair value of assets acquired (excluding cash acquired of $11.8 million)	28,966	0
Fair value of liabilities assumed	16,837	0
Non-cash financing activities:
Payables recorded under contingent payment arrangements	17,384	0
Company-sponsored investment funds
Adjustments to reconcile net income to net cash provided by operating activities:
Unrealized (gains) losses on investments	(29,522)	(23,755)
Changes in assets and liabilities:
Decrease (increase) in investments	(155,064)	966,737
(Increase) decrease in other assets	1,903	(663,220)
Cash flows from financing activities:
Subscriptions (redemptions) of investments in consolidated company-sponsored investment funds, net	$ 123,677	$ (518,601)