Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 168,749	$ 159,230
Other comprehensive income (loss):
Foreign currency translation adjustments, before tax	(21,396)	2,630
Income tax benefit (expense)	73	(77)
Foreign currency translation adjustments, net of tax	(21,323)	2,553
Changes in employee benefit related items:
Amortization of prior service cost	6	6
Recognized actuarial gain	325	267
Changes in employee benefit related items	331	273
Income tax (expense) benefit	(77)	10
Employee benefit related items, net of tax	254	283
Other comprehensive (loss) income	(21,069)	2,836
Less: Comprehensive (loss) income in consolidated entities attributable to non-controlling interests	(25,571)	10,096
Comprehensive income attributable to AB Unitholders	$ 173,251	$ 151,970