SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Allowance for Loan Loss (Details)	12 Months Ended
Dec. 31, 2019
Allowance for Loan Loss
Period considered for charge-off trends utilized for analyzing actual charge-offs	3 months

Represents the prior period considered for charge-off trends utilized in analyzing the actual charge-offs.

No definition available.

Name:	ads_ChargeOffTrendUsedToAnalyzeActualChargeOffsPeriod
Namespace Prefix:	ads_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration