Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ 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
Quarterly Financial Information Disclosure [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
Net income		$ 80,022		$ 59,828		$ 52,274		$ 46,439		$ 59,880		$ 65,900		$ 58,457		$ 58,160		$ 238,563	$ 242,397	$ 207,422
Basic net income per unit (in dollars per unit)		$ 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 net income per unit (in dollars per unit)		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
Cash distributions per unit (in dollars per unit)	[2],[3]	$ 0.85		$ 0.63		$ 0.56		$ 0.49		$ 0.64		$ 0.69		$ 0.62		$ 0.73

[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.

[2] Cash distributions reflect the impact of AB’s non-GAAP adjustments.

[3] Declared and paid during the following quarter.