Investment in AB (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Jun. 30, 2016	Sep. 30, 2016	Sep. 30, 2015
Change in Equity Method Investment [Roll Forward]
Investment in AB, beginning of period			$ 1,576,120	$ 1,576,120
Equity in net income attributable to AB Unitholders	$ 55,925	$ 48,387	$ 104,834	160,759	$ 153,194
Changes in accumulated other comprehensive income (loss)	634	$ (2,198)		1,433	(4,314)
Additional investments with proceeds from exercise of compensatory options to buy AB Holding Units				2,371	8,979
Cash distributions received from AB				(143,982)	(168,505)
Capital contributions from AB				(345)	$ (733)
AB Holding Units retired				(135,943)
AB Holding Units issued to fund long-term incentive compensation plans				15,199
Change in AB Holding Units held by AB for long-term incentive compensation plans				(696)
Investment in AB, end of period	$ 1,474,916			$ 1,474,916