Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended																12 Months Ended
		Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Equity in net income attributable to AB Unitholders		$ 85,725		$ 49,055		$ 47,947		$ 49,666		$ 78,630		$ 55,925		$ 44,657		$ 60,177		$ 232,393	$ 239,389	$ 210,084
Net income		$ 78,593		$ 43,178		$ 41,741		$ 43,910		$ 72,664		$ 50,258		$ 39,072		$ 54,592		$ 207,422	$ 216,586	$ 185,764
Basic net income per unit (in dollars per unit)		$ 0.84	[1]	$ 0.46	[1]	$ 0.43	[1]	$ 0.46	[1]	$ 0.77	[1]	$ 0.52	[1]	$ 0.40	[1]	$ 0.55	[1]	$ 2.19	$ 2.24	$ 1.87
Diluted net income per unit (in dollars per unit)		0.84	[1]	0.46	[1]	0.43	[1]	0.46	[1]	0.77	[1]	0.52	[1]	0.40	[1]	0.55	[1]	$ 2.19	$ 2.23	$ 1.86
Cash distributions per unit (in dollars per unit)	[2],[3]	$ 0.84		$ 0.51		$ 0.49		$ 0.46		$ 0.67		$ 0.45		$ 0.40		$ 0.40

[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.