Long-term Incentive Compensation Plans - Schedule of Share-based Compensation, Employee Stock Purchase Plan, Activity (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Share-Based Payment Arrangement [Abstract]
Total amount of AB Holding Units Purchased (in shares)	1.1	1.8	2.1	2.3
Total Cash Paid for AB Holding Units Purchased	$ 38.6	$ 56.9	$ 71.7	$ 75.7
Open Market Purchases of AB Holding Units Purchased (in shares)	1.1	1.8	1.8	1.8
Total Cash Paid for Open Market Purchases of AB Holding Units	$ 38.6	$ 56.9	$ 60.1	$ 56.9