Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net income	$ 206,846	$ 156,255
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred sales commissions	6,598	9,079
Non-cash long-term incentive compensation expense	12,484	7,693
Depreciation and other amortization	17,737	16,282
Unrealized (gains) losses on investments	3,239	(16,397)
Other, net	(2,885)	3,528
Changes in assets and liabilities:
(Increase) in segregated cash and securities	(208,179)	(309,729)
(Increase) in receivables	(140,399)	(206,909)
Decrease (increase) in investments	35,028	20,497
Decrease in deferred sales commissions	348	821
(Increase) decrease in other assets	(68,129)	(32,109)
Increase in payables	425,449	502,976
Increase (decrease) in accounts payable and accrued expenses	5,073	(30,810)
Increase in accrued compensation and benefits	66,012	80,054
Net cash provided by operating activities	164,713	156,956
Cash flows from investing activities:
Purchases of furniture, equipment and leasehold improvements	(5,440)	(6,525)
Net cash used in investing activities	(5,440)	(6,525)
Cash flows from financing activities:
(Repayment) issuance of commercial paper, net	(3,069)	93,581
Repayment of bank loans	(75,000)	0
Increase in overdrafts payable	7,410	50,377
Distributions to General Partner and Unitholders	(247,773)	(198,040)
Capital contributions to non-controlling interests in consolidated entities	(5)	(3,137)
Capital contributions to affiliates	(1,677)	(81)
Additional investments by AB Holding with proceeds from exercise of compensatory options to buy AB Holding Units	4,009	4,468
Purchases of AB Holding Units to fund long-term incentive compensation plan awards, net	(2,128)	(30,833)
Other	21	(412)
Net cash provided by (used in) financing activities	54,573	(88,113)
Effect of exchange rate changes on cash and cash equivalents	8,261	8,049
Net increase in cash and cash equivalents	222,107	70,367
Cash and cash equivalents as of beginning of the period	998,448	994,510
Cash and cash equivalents as of end of the period	1,220,555	1,064,877
Company-sponsored investment funds
Adjustments to reconcile net income to net cash provided by operating activities:
Unrealized (gains) losses on investments	(23,393)	(26,834)
Changes in assets and liabilities:
Decrease (increase) in investments	(686,794)	(153,512)
(Increase) decrease in other assets	515,678	136,071
Cash flows from financing activities:
Subscriptions (redemptions) of investments in consolidated company-sponsored investment funds, net	372,785	$ (4,036)
Cash and cash equivalents as of beginning of the period	326,518
Cash and cash equivalents as of end of the period	$ 580,721