Long-term Incentive Compensation Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
AB Holding Units purchased (in units)	4,300,000	1,900,000	5,700,000	3,800,000
Amount paid for AB Holding Units acquired	$ 96,700	$ 44,300	$ 127,800	$ 84,000
Open-market purchases of AB Holding Units (in units)	3,700,000	1,900,000	4,900,000	3,700,000
Amount paid for open-market purchases of AB Holding Units	$ 82,400	$ 43,900	$ 110,300	$ 82,000
Restricted AB Holding Units awarded to employees (in units)			2,000,000	300,000
Units issued upon exercise of options (in units)			545,458	100,000
Proceeds from stock options exercised			$ 9,246	$ 2,377