Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net income	$ 466,007	$ 463,611
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred sales commissions	25,015	31,606
Non-cash long-term incentive compensation expense	26,947	6,530
Depreciation and other amortization	49,995	44,010
Unrealized (gains) losses on investments	3,323	(27,659)
Other, net	10,195	8,099
Changes in assets and liabilities:
Decrease in segregated cash and securities	161,531	73,252
Decrease (increase) in receivables	8,079	(206,052)
Decrease (increase) in investments	(76,780)	184,655
Decrease (increase) in deferred sales commissions	1,871	(2,171)
(Increase) decrease in other assets	(33,003)	(40,933)
(Decrease) increase in payables	(58,126)	268,937
Increase in accounts payable and accrued expenses	23,982	59,950
Increase in accrued compensation and benefits	358,586	322,600
Net cash provided by operating activities	1,080,878	1,141,905
Cash flows from investing activities:
Purchases of investments	(11)	0
Proceeds from sales of investments	10	191
Purchases of furniture, equipment and leasehold improvements	(24,952)	(28,318)
Proceeds from sales of furniture, equipment and leasehold improvements	39	14
Purchase of business, net of cash acquired	0	(20,541)
Net cash used in investing activities	(24,914)	(48,654)
Cash flows from financing activities:
(Repayment) of commercial paper, net	(220,363)	(197,064)
Increase (decrease) in overdrafts payable	66,134	(74,837)
Distributions to General Partner and Unitholders	(489,049)	(400,441)
Capital contributions (to) from non-controlling interests in consolidated entities	(43,217)	364
Purchase of non-controlling interest	(1,833)	0
Capital contributions from affiliates	79	439
Payments of contingent payment arrangements/purchases of shares	(6,344)	(4,994)
Additional investments by AB Holding with proceeds from exercise of compensatory options to buy AB Holding Units	17,672	2,371
Purchases of AB Holding Units to fund long-term incentive compensation plan awards, net	(134,186)	(128,778)
Purchases of AB Units	(993)	(359)
Other	0	(19)
Net cash used in financing activities	(820,473)	(839,544)
Effect of exchange rate changes on cash and cash equivalents	17,458	7,155
Net increase in cash and cash equivalents	252,949	260,862
Cash and cash equivalents as of beginning of the period	994,510	577,300
Cash and cash equivalents as of end of the period	1,247,459	838,162
Company-sponsored investment funds
Adjustments to reconcile net income to net cash provided by operating activities:
Unrealized (gains) losses on investments	(33,062)	(16,675)
Changes in assets and liabilities:
Consolidation of cash and cash equivalents of consolidated company-sponsored investment funds	0	8,512
Decrease (increase) in investments	(192,797)	(34,576)
(Increase) decrease in other assets	339,115	(1,791)
Cash flows from financing activities:
Redemptions of non-controlling interests of consolidated company-sponsored investment funds, net	(8,373)	$ (36,226)
Cash and cash equivalents as of beginning of the period	337,525
Cash and cash equivalents as of end of the period	$ 445,250