Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 779,498	$ 720,800	$ 694,846
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred sales commissions	21,343	31,886	41,066
Non-cash long-term incentive compensation expense	187,514	185,234	152,162
Depreciation and other amortization	70,000	66,999	59,026
Unrealized losses (gains) on investments	23,164	3,554	(28,204)
Losses on real estate asset write-offs	38	8,161	5,456
Other, net	(6,484)	5,028	3,629
Changes in assets and liabilities:
(Increase) decrease in securities, segregated	(353,204)	129,747	(380,823)
(Increase) decrease in receivables	(207,000)	67,539	(296,233)
(Increase) decrease in investments	(294,383)	293	187,752
(Increase) decrease in deferred sales commissions	(8,365)	1,878	(5,886)
(Increase) decrease in other assets	(152,726)	(2,255)	13,517
Increase (decrease) in payables	1,024,317	(338,523)	886,520
(Decrease) increase in accounts payable and accrued expenses	(11,225)	10,657	2,459
Increase (decrease) in accrued compensation and benefits	4,341	12,187	(3,238)
Net cash provided by operating activities	1,308,481	645,452	1,548,048
Cash flows from investing activities:
Purchases of investments	0	(12)	0
Proceeds from sales of investments	0	11	372
Purchases of furniture, equipment and leasehold improvements	(32,789)	(39,417)	(36,728)
Proceeds from sales of furniture, equipment and leasehold improvements	0	75	15
Purchase of intangible asset	0	0	(2,500)
Purchase of businesses, net of cash acquired	0	0	(20,541)
Net cash used in investing activities	(32,789)	(39,343)	(59,382)
Cash flows from financing activities:
Issuance (repayment) of commercial paper, net	24,546	(28,553)	(72,003)
(Repayment) proceeds from bank loans	(50,000)	75,000	0
Increase (decrease) in overdrafts payable	3,273	63,393	(84,512)
Distributions to General Partner and Unitholders	(858,193)	(644,139)	(537,564)
(Redemptions) purchases of non-controlling interests of consolidated company-sponsored investment funds, net	(638)	(43,217)	364
Capital contributions (to) from affiliates	(1,421)	366	1,000
Payments of contingent payment arrangements/purchase of shares	(1,093)	(7,592)	(5,545)
Additional investments by AB Holding with proceeds from exercise of compensatory options to buy AB Holding Units	16,589	20,110	6,108
Purchases of AB Holding Units to fund long-term incentive compensation plan awards, net	(267,427)	(219,627)	(235,893)
Purchases of AB Units	(153)	(1,003)	(374)
Other	(1,998)	(1,833)	(22)
Net cash used in financing activities	(1,608,658)	(623,931)	(1,061,278)
Effect of exchange rate changes on cash and cash equivalents	(12,158)	21,760	(10,178)
Net (decrease) increase in cash and cash equivalents	(345,124)	3,938	417,210
Cash and cash equivalents as of beginning of the period	998,448	994,510	577,300
Cash and cash equivalents as of beginning of the period			994,510
Cash and cash equivalents as of end of the period	653,324	998,448	994,510
Cash paid:
Interest paid	60,286	30,975	11,148
Income taxes paid	41,946	67,421	27,387
Non-cash investing activities:
Fair value of assets acquired	0	0	33,583
Fair value of liabilities assumed	0	0	1,149
Non-cash financing activities:
Payables recorded under contingent payment arrangements	0	0	11,893
Consolidated Company-Sponsored Investment Funds
Adjustments to reconcile net income to net cash provided by operating activities:
Unrealized losses (gains) on investments	(14,217)	(36,340)	(29,121)
Changes in assets and liabilities:
Consolidation of cash and cash equivalents of consolidated company-sponsored investment funds	0	0	358,534
(Increase) decrease in investments	908,804	(639,067)	(342,938)
(Increase) decrease in other assets	(662,934)	417,674	229,524
Cash flows from financing activities:
(Redemptions) purchases of non-controlling interests of consolidated company-sponsored investment funds, net	(472,143)	163,164	$ (132,837)
Cash and cash equivalents as of beginning of the period	326,518
Cash and cash equivalents as of end of the period	$ 13,118	$ 326,518