Long-term Incentive Compensation Plans (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Employee allocation percentage maximum					50.00%	50.00%
Long-term incentive cash maximum per employee					$ 250,000	$ 250,000
Long-term incentive awards vesting period			4 years
Period over which holding units are typically distributed to directors			3 years
AB Holding Units purchased in periods	100,000	15,000	800,000	200,000
Dollar amount paid for AB Holding Units acquired	$ 4,300,000	$ 400,000	$ 21,300,000	$ 4,100,000
Open-market purchases of AB Holding Units (in units)	100,000		700,000
Dollar amount paid for open-market purchases of AB Holding Units	$ 4,000,000		$ 19,000,000
Restricted AB Holding Units awarded to employees			300,000	400,000
Units issued upon exercise of options			526,201	700,000
Proceeds from stock options exercised			$ 8,979,000	$ 12,026,000
Employees Based Outside of the United States [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Employee allocation percentage maximum					100.00%	100.00%
Long-term incentive cash maximum per employee					$ 100,000	$ 100,000