Investment in AB (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Change in Equity Method Investment [Roll Forward]
Beginning balance	$ 1,623,764
Equity in net income attributable to AB Unitholders	94,353	$ 88,907
Changes in accumulated other comprehensive (loss)	(4,204)	(3,036)
Cash distributions received from AB	(136,714)	$ (106,091)
Capital contributions from AB	(529)
AB Holding Units retired	(11,707)
AB Holding Units issued to fund long-term incentive compensation plans	27,362
Change in AB Holding Units held by AB for long-term incentive compensation plans	(4,093)
Ending balance	$ 1,588,232

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