Long-term Incentive Compensation Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Payment Arrangement [Abstract]
Holding units purchased in period (in units)	900,000	2,000,000.0
Dollar amount paid for holding units acquired	$ 19,800	$ 58,600
Open-market purchases of holding units (in units)	800,000	1,900,000
Dollar amount paid for open-market purchases of holding units	$ 17,300	$ 55,200
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units issued upon options exercised (in units)	5,182	300,000
Proceeds from stock options exercised	$ 147	$ 7,382
Employees and Eligible Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted AB Holding Unit awards granted to employees and Eligible Directors (in units)	100,000	100,000