Net Income per Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Unit [Abstract]
Net income – basic	$ 41,741	$ 39,072	$ 85,651	$ 93,664
Additional allocation of equity in net income attributable to AB resulting from assumed dilutive effect of compensatory options	137	189	313	361
Net income – diluted	$ 41,878	$ 39,261	$ 85,964	$ 94,025
Weighted average units outstanding – basic (in units)	96,061,000	97,463,000	96,150,000	98,530,000
Dilutive effect of compensatory options (in units)	430,000	650,000	482,000	534,000
Weighted average units outstanding – diluted (in units)	96,491,000	98,113,000	96,632,000	99,064,000
Basic net income per unit (in dollars per unit)	$ 0.43	$ 0.40	$ 0.89	$ 0.95
Diluted net income per unit (in dollars per unit)	$ 0.43	$ 0.40	$ 0.89	$ 0.95
Anti-dilutive units excluded from diluted net income computation (in units)	2,507,179	2,793,454	2,452,633	2,873,106