Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 181,926	$ 152,272	$ 388,772	$ 308,527
Other comprehensive income (loss):
Foreign currency translation adjustment, before reclassification and tax	(20,656)	7,355	(10,735)	16,356
Less: reclassification adjustment for (losses) included in net income upon liquidation	(100)	0	(100)	0
Foreign currency translation adjustments, before tax	(20,556)	7,355	(10,635)	16,356
Income tax benefit	0	134	0	0
Foreign currency translation adjustments, net of tax	(20,556)	7,489	(10,635)	16,356
Unrealized gains on investments:
Unrealized gains arising during period	0	26	0	10
Less: reclassification adjustment for gains included in net income	0	0	0	0
Change in unrealized gains on investments	0	26	0	10
Income tax benefit (expense)	0	0	0	(2)
Unrealized gains on investments, net of tax	0	26	0	8
Changes in employee benefit related items:
Amortization of prior service cost	5	6	11	12
Recognized actuarial gain	286	264	568	523
Changes in employee benefit related items	291	270	579	535
Income tax benefit (expense)	2	(3)	(116)	(79)
Employee benefit related items, net of tax	293	267	463	456
Other	374	0	374	0
Other comprehensive (loss) income	(19,889)	7,782	(9,798)	16,820
Less: Comprehensive income in consolidated entities attributable to non-controlling interests	220	18,042	22,887	34,436
Comprehensive income attributable to AB Unitholders	$ 161,817	$ 142,012	$ 356,087	$ 290,911