Investment in AB (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Change in Equity Method Investment [Roll Forward]
Investment in AB as of December 31, 2016			$ 1,540,508
Equity in net income attributable to AB Unitholders	$ 49,055	$ 55,925	146,668	$ 160,759
Changes in accumulated other comprehensive income (loss)	2,760	$ 634	9,172	1,433
Additional investments with proceeds from exercise of compensatory options to buy AB Holding Units			17,672	2,371
Cash distributions received from AB			(173,025)	(143,982)
Capital contributions from AB			(265)	$ (345)
AB Holding Units retired			(138,954)
AB Holding Units issued to fund long-term incentive compensation plans			45,176
Change in AB Holding Units held by AB for long-term incentive compensation plans			(5,280)
Investment in AB as of September 30, 2017	$ 1,441,672		$ 1,441,672