Long-term Incentive Compensation Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
AB Holding Units purchased (in units)	1,300,000	1,900,000
Amount paid for AB Holding Units acquired	$ 31,000	$ 39,700
Open-market purchases of AB Holding Units (in units)	1,200,000	1,800,000
Amount paid for open-market purchases of AB Holding Units	$ 27,800	$ 38,100
Restricted AB Holding Units awarded to employees (in units)	1,100,000	300,000
Units issued upon exercise of options (in units)	262,819	100,000
Proceeds from stock options exercised	$ 4,468	$ 1,457