Statements of Income - USD ($) $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Equity in net income attributable to AB Unitholders	$ 87,909		$ 66,722		$ 59,023		$ 52,638		$ 66,759		$ 72,802		$ 65,388		$ 65,698		$ 266,292	$ 270,647	$ 232,393
Income taxes																	27,729	28,250	24,971
Net income	$ 80,022		$ 59,828		$ 52,274		$ 46,439		$ 59,880		$ 65,900		$ 58,457		$ 58,160		$ 238,563	$ 242,397	$ 207,422
Net income per unit:
Basic (in dollars per share)	$ 0.84	[1]	$ 0.62	[1]	$ 0.54	[1]	$ 0.49	[1]	$ 0.63	[1]	$ 0.68	[1]	$ 0.59	[1]	$ 0.60	[1]	$ 2.49	$ 2.50	$ 2.19
Diluted (in dollars per share)	$ 0.84	[1]	$ 0.62	[1]	$ 0.54	[1]	$ 0.49	[1]	$ 0.63	[1]	$ 0.68	[1]	$ 0.59	[1]	$ 0.60	[1]	$ 2.49	$ 2.50	$ 2.19

[1] Basic and diluted net income per unit are computed independently for each of the periods presented. Accordingly, the sum of the quarterly net income per unit amounts may not agree to the total for the year.