Investment in AB (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Change in Equity Method Investment [Roll Forward]
Investment in AB, beginning of period			$ 1,540,508
Equity in net income attributable to AB Unitholders	$ 47,947	$ 44,657	97,613	$ 104,834
Changes in accumulated other comprehensive income (loss)	3,177	$ (1,273)	6,412	799
Additional investments with proceeds from exercise of compensatory options to buy AB Holding Units			9,246	2,377
Cash distributions received from AB			(120,816)	(99,720)
Capital contributions from AB			(589)	$ (643)
AB Holding Units retired			(128,108)
AB Holding Units issued to fund long-term incentive compensation plans			43,524
Change in AB Holding Units held by AB for long-term incentive compensation plans			(6,732)
Investment in AB, end of period	$ 1,441,058		$ 1,441,058