Investment in AB (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Equity Method Investments and Joint Ventures [Abstract]
Investment in AB, beginning of period			$ 1,627,740
Equity in net income attributable to AB Unitholders	$ 48,988	$ 49,876	155,013	$ 139,714
Changes in accumulated other comprehensive income (loss)	(2,198)	$ (5,632)	(4,314)	(3,922)
Additional investments with proceeds from exercise of compensatory options to buy AB Holding Units			8,979	12,849
Cash distributions received from AB			(168,505)	(154,454)
Capital contributions from AB			(733)	$ (1,411)
AB Holding Units retired			(102,678)
AB Holding Units issued to fund long-term incentive compensation plans			7,553
Change in AB Holding Units held by AB for long-term incentive compensation plans			2,544
Investment in AB, end of period	$ 1,525,599		$ 1,525,599