Investment in AB (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 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	49,666	$ 60,177
Changes in accumulated other comprehensive income (loss)	3,235	2,072
Additional investments with proceeds from exercise of compensatory options to buy AB Holding Units	4,468	1,457
Cash distributions received from AB	(70,381)	(55,868)
Capital contributions from AB	(518)	$ 6,115
AB Holding Units retired	(31,906)
AB Holding Units issued to fund long-term incentive compensation plans	21,668
Change in AB Holding Units held by AB for long-term incentive compensation plans	(4,569)
Investment in AB, end of period	$ 1,512,171