Long-term Incentive Compensation Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
AB Holding Units purchased in periods	1,900,000	700,000
Dollar amount paid for AB Holding Units acquired	$ 39,700	$ 17,000
Open-market purchases of AB Holding Units (in units)	1,800,000	600,000
Dollar amount paid for open-market purchases of AB Holding Units	$ 38,100	$ 15,100
Restricted AB Holding Units awarded to employees	300,000	100,000
Units issued upon exercise of options	85,471	200,000
Proceeds from stock options exercised	$ 1,457	$ 3,901