Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 208,057	$ 191,956	$ 575,067	$ 525,195
Other comprehensive income (loss):
Foreign currency translation adjustments, before tax	16,440	(12,694)	1,361	(12,242)
Income tax (expense) benefit	(98)	189	42	39
Foreign currency translation adjustments, net of tax	16,342	(12,505)	1,403	(12,203)
Changes in employee benefit related items:
Amortization of prior service cost	6	6	18	18
Recognized actuarial gain	325	288	975	840
Changes in employee benefit related items	331	294	993	858
Income tax (expense) benefit	(2)	253	(80)	288
Employee benefit related items, net of tax	329	547	913	1,146
Other comprehensive income (loss)	16,671	(11,958)	2,316	(11,057)
Less: Comprehensive income (loss) in consolidated entities attributable to non-controlling interests	81	4,295	(4,550)	22,165
Comprehensive income attributable to AB Unitholders	$ 224,647	$ 175,703	$ 581,933	$ 491,973