Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 191,956	$ 204,400	$ 525,195	$ 593,172
Other comprehensive income (loss):
Foreign currency translation adjustment, before reclassification and tax	(12,694)	(4,154)	(12,242)	(14,889)
Less: reclassification adjustment for (losses) included in net income upon liquidation	0	0	0	(100)
Foreign currency translation adjustments, before tax	(12,694)	(4,154)	(12,242)	(14,789)
Income tax benefit	189	0	39	0
Foreign currency translation adjustments, net of tax	(12,505)	(4,154)	(12,203)	(14,789)
Changes in employee benefit related items:
Amortization of prior service cost	6	6	18	17
Recognized actuarial gain	288	285	840	853
Changes in employee benefit related items	294	291	858	870
Income tax benefit (expense)	253	(5)	288	(121)
Employee benefit related items, net of tax	547	286	1,146	749
Other	0	0	0	374
Other comprehensive (loss) income	(11,958)	(3,868)	(11,057)	(13,666)
Less: Comprehensive income in consolidated entities attributable to non-controlling interests	4,295	721	22,165	23,608
Comprehensive income attributable to AB Unitholders	$ 175,703	$ 199,811	$ 491,973	$ 555,898