Net Income Per Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016	[1]	Mar. 31, 2016	[1]	Dec. 31, 2015	[1]	Sep. 30, 2015	[1]	Jun. 30, 2015	[1]	Mar. 31, 2015	[1]	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net income - basic	$ 72,664		$ 50,258		$ 39,072		$ 54,592		$ 51,087		$ 42,086		$ 47,614		$ 44,977		$ 216,586	$ 185,764	$ 178,468
Additional allocation of equity in net income attributable to AB resulting from assumed dilutive effect of compensatory options																	878	1,383	1,518
Net income - diluted																	$ 217,464	$ 187,147	$ 179,986
Weighted average units outstanding - basic (in units)																	96,834,000	99,475,000	96,802,000
Dilutive effect of compensatory options (in units)																	554,000	1,037,000	1,148,000
Weighted average units outstanding - diluted (in units)																	97,388,000	100,512,000	97,950,000
Basic net income per unit (in dollars per unit)	$ 0.77	[1],[2]	$ 0.52	[1],[2]	$ 0.40	[2]	$ 0.55	[2]	$ 0.53	[2]	$ 0.42	[2]	$ 0.47	[2]	$ 0.45	[2]	$ 2.24	$ 1.87	$ 1.84
Diluted net income per unit (in dollars per unit)	$ 0.77	[1],[2]	$ 0.52	[1],[2]	$ 0.40	[2]	$ 0.55	[2]	$ 0.52	[2]	$ 0.42	[2]	$ 0.47	[2]	$ 0.45	[2]	$ 2.23	$ 1.86	$ 1.84
Antidilutive securities																	2,873,106	2,409,499	2,806,033

[1] Certain prior-period amounts have been revised, see Note 2 for a discussion of the revision.

[2] Basic and diluted net income per unit are computed independently for each of the periods presented. Accordingly, the sum of the quarterly net income per unit amounts may not agree to the total for the year.