Statements of Income - USD ($) $ 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
Income Statement [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
Income taxes																	24,971	22,803	24,320
Net income	$ 78,593		$ 43,178		$ 41,741		$ 43,910		$ 72,664		$ 50,258		$ 39,072		$ 54,592		$ 207,422	$ 216,586	$ 185,764
Net income per unit:
Basic (in dollars per share)	$ 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 (in dollars per share)	$ 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

[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.