Long-term Incentive Compensation Plans - Unit Purchase Activity (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Share-Based Payment Arrangement [Abstract]
Total amount of AB Holding Units Purchased (in shares)	0.9	0.0	1.0	0.5
Total Cash Paid for AB Holding Units Purchased	$ 29.0	$ 0.0	$ 33.3	$ 18.8
Open Market Purchases of AB Holding Units Purchased (in shares)	0.6	0.0	0.6	0.0
Total Cash Paid for Open Market Purchases of AB Holding Units	$ 21.5	$ 0.0	$ 21.5	$ 0.0