Long-term Incentive Compensation Plans - Unit Purchase Activity (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Share-Based Payment Arrangement [Abstract]
Total amount of AB Holding Units Purchased/Retained (in shares)	2.3	0.9	2.6	1.9
Total Cash Paid for AB Holding Units Purchased/Retained	$ 92.7	$ 38.3	$ 106.7	$ 75.7
Open Market Purchases of AB Holding Units Purchased (in shares)	2.3	0.8	2.3	1.4
Total Cash Paid for Open Market Purchases of AB Holding Units	$ 92.7	$ 34.6	$ 92.7	$ 58.8