Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash flows from operating activities:
Net income	$ 295,165	$ 298,513
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred sales commissions	21,819	25,112
Non-cash long-term incentive compensation expense	4,383	9,682
Depreciation and other amortization	29,548	28,391
Unrealized gains on investments	(17,517)	(4,826)
Other, net	9,091	(8,486)
Changes in assets and liabilities:
(Increase) decrease in segregated cash and securities	(100,895)	8,821
(Increase) in receivables	(382,084)	(87,105)
Decrease (increase) in investments	147,317	56,117
(Increase) in deferred sales commissions	(1,837)	(26,475)
(Increase) in other assets	(62,693)	(60,687)
Increase (decrease) in payables	336,812	(18,922)
Increase (decrease) in accounts payable and accrued expenses	67,807	(14,931)
Increase in accrued compensation and benefits	176,636	230,865
Net cash provided by operating activities	514,578	436,069
Cash flows from investing activities:
Purchases of investments	0	(88)
Proceeds from sales of investments	92	0
Purchases of furniture, equipment and leasehold improvements	(20,304)	(11,730)
Proceeds from sales of furniture, equipment and leasehold improvements	0	33
Net cash used in investing activities	(20,212)	(11,785)
Cash flows from financing activities:
(Repayment) of commercial paper, net	(46,144)	(84,907)
Proceeds from bank loans	50,000	50,000
Increase in overdrafts payable	47,630	28,901
Distributions to General Partner and Unitholders	(275,930)	(313,597)
Redemptions of non-controlling interests of consolidated VIEs, net	0	430
Capital contributions (to) from affiliates	(120)	793
Payments of contingent payment arrangements	(538)	(404)
Additional investments by AB Holding with proceeds from exercise of compensatory options to buy AB Holding Units	2,377	8,979
Purchases of AB Holding Units to fund long-term incentive compensation plan awards, net	(83,744)	(19,709)
Purchases of AB Units	(337)	(726)
Other	(11)	(14)
Net cash used in financing activities	(352,351)	(330,254)
Effect of exchange rate changes on cash and cash equivalents	6,324	(4,176)
Net increase in cash and cash equivalents	148,339	89,854
Cash and cash equivalents as of beginning of the period	577,300	555,503
Cash and cash equivalents as of end of the period	725,639	645,357
Consolidated Variable Interest Entities
Adjustments to reconcile net income to net cash provided by operating activities:
Unrealized gains on investments	2,599	0
Changes in assets and liabilities:
Decrease (increase) in investments	(10,630)	0
(Increase) in other assets	(943)	0
Cash flows from financing activities:
Redemptions of non-controlling interests of consolidated VIEs, net	(45,534)	0
Cash and cash equivalents as of beginning of the period	0
Cash and cash equivalents as of end of the period	35,076
Supplemental information - consolidation of variable interest entities:
Consolidation of cash and cash equivalents of consolidated variable interest entities	35,817	0
Consolidation of investments of consolidated variable interest entities	215,175	0
Consolidation of other assets of consolidated variable interest entities	13,871	0
Consolidation of other liabilities of consolidated variable interest entities	14,012	0
Consolidation of redeemable non-controlling interest of consolidated variable interest entities	$ 250,851	$ 0