Valuation and Qualifying Account - Allowance for Doubtful Accounts (Details) - SEC Schedule, 12-09, Allowance, Credit Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Movement in Valuation Allowances and Reserves
Balance at Beginning of Period	$ 309		$ 395		$ 411
Credited to Costs and Expenses	100		132		0
Deductions	98	[1]	218	[2]	16	[3]
Balance at End of Period	311		309		395
AllianceBernstein L.P.
Movement in Valuation Allowances and Reserves
Amounts written-off as uncollectible	$ 98		$ 218		$ 16

[1] Includes accounts written-off as uncollectible of $98.

[2] Includes accounts written-off as uncollectible of $218

[3] Includes accounts written-off as uncollectible of $16.