Long-term Incentive Compensation Plans - Unit Purchase Activity (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]
Total amount of AB Holding Units Purchased/Retained (in shares)	1.8	0.0	2.3	2.6
Total Cash Paid for AB Holding Units Purchased/Retained	$ 56.9	$ 1.0	$ 75.7	$ 107.7
Open Market Purchases of AB Holding Units Purchased (in shares)	1.8	0.0	1.8	2.3
Total Cash Paid for Open Market Purchases of AB Holding Units	$ 56.9	$ 0.0	$ 56.9	$ 92.7