Long-Term Incentive Compensation Plans - Summary of Changes in Unvested Restricted AB Holding Units (Details) - Restricted Stock Units (RSUs)	12 Months Ended
	Dec. 31, 2018 $ / shares shares
AB Holding Units
Unvested as of December 31, 2017 (in units) | shares	19,072,910
Granted (in units) | shares	9,123,321
Vested (in units) | shares	(7,128,611)
Forfeited (in units) | shares	(853,231)
Unvested as of December 31, 2018 (in units) | shares	20,214,389
Weighted Average Grant Date Fair Value per AB Holding Unit
Unvested as of December 31, 2017, Weighted Average Grant Date Fair Value per AB Holding Unit (in dollars per unit) | $ / shares	$ 23.82
Granted, Weighted Average Grant Date Fair Value per AB Holding Unit (in dollars per unit) | $ / shares	26.64
Vested, Weighted Average Grant Date Fair Value per AB Holding Unit (in dollars per unit) | $ / shares	23.72
Forfeited, Weighted Average Grant Date Fair Value per AB Holding Unit (in dollars per unit) | $ / shares	24.02
Unvested as of December 31, 2018, Weighted Average Grant Date Fair Value per AB Holding Unit (in dollars per unit) | $ / shares	$ 25.12