Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net income	$ 308,527	$ 289,880
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred sales commissions	17,386	21,819
Non-cash long-term incentive compensation expense	21,337	4,383
Depreciation and other amortization	33,313	29,548
Unrealized (gains) losses on investments	2,636	(17,517)
Other, net	5,712	9,091
Changes in assets and liabilities:
(Increase) in segregated cash and securities	(131,552)	(100,895)
(Increase) in receivables	(50,545)	(382,084)
Decrease (increase) in investments	(37,978)	147,317
Decrease (increase) in deferred sales commissions	1,923	(1,837)
(Increase) decrease in other assets	(68,430)	(62,693)
Increase in payables	70,082	336,812
(Decrease) increase in accounts payable and accrued expenses	(11,189)	73,092
Increase in accrued compensation and benefits	201,417	176,636
Net cash provided by operating activities	448,239	514,578
Cash flows from investing activities:
Purchases of investments	(11)	0
Proceeds from sales of investments	10	92
Purchases of furniture, equipment and leasehold improvements	(14,023)	(20,304)
Proceeds from sales of furniture, equipment and leasehold improvements	39	0
Net cash used in investing activities	(13,985)	(20,212)
Cash flows from financing activities:
(Repayment) of commercial paper, net	(33,709)	(46,144)
Proceeds from bank loans	30,000	50,000
Increase in overdrafts payable	68,504	47,630
Distributions to General Partner and Unitholders	(339,139)	(275,930)
Capital contributions to non-controlling interests in consolidated entities	(7,869)	0
Purchase of non-controlling interest	(1,833)	0
Capital contributions to affiliates	(280)	(120)
Payments of contingent payment arrangements	(812)	(538)
Additional investments by AB Holding with proceeds from exercise of compensatory options to buy AB Holding Units	9,246	2,377
Purchases of AB Holding Units to fund long-term incentive compensation plan awards, net	(127,472)	(83,744)
Purchases of AB Units	(684)	(337)
Other	5	(11)
Net cash used in financing activities	(476,775)	(352,351)
Effect of exchange rate changes on cash and cash equivalents	11,179	6,324
Net (decrease) increase in cash and cash equivalents	(31,342)	148,339
Cash and cash equivalents as of beginning of the period	994,510	577,300
Cash and cash equivalents as of end of the period	963,168	725,639
Company-sponsored investment funds
Adjustments to reconcile net income to net cash provided by operating activities:
Unrealized (gains) losses on investments	(18,550)	2,599
Changes in assets and liabilities:
Decrease (increase) in investments	(66,710)	(10,630)
(Increase) decrease in other assets	170,860	(943)
Cash flows from financing activities:
Redemptions of non-controlling interests of consolidated company-sponsored investment funds, net	(72,732)	$ (45,534)
Cash and cash equivalents as of beginning of the period	337,525
Cash and cash equivalents as of end of the period	$ 364,777