Name:	atch_CashAndSecuritiesSegregatedUnderFederalAndOtherRegulationsLineItems
Namespace Prefix:	atch_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Represents the cash on deposit in the reserve account in excess of the amount required in accordance with federal regulations.

No definition available.

Name:	atch_CashReserveDepositInExcessOfAmountRequired
Namespace Prefix:	atch_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the cash on deposit in the reserve account less than the amount required in accordance with federal regulations.

No definition available.

Name:	atch_CashReserveDepositLessThanAmountRequired
Namespace Prefix:	atch_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Cash reserve required in a special reserve account for the exclusive benefit of customers pursuant to SEC Regulations.

No definition available.

Name:	atch_CashReserveDepositRequired
Namespace Prefix:	atch_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of cash subject to withdrawal restrictions, restricted deposits held as compensating balances, and cash and securities segregated in compliance with regulations (such as cash deposited in a special reserve account for the exclusive benefit of customers).

No definition available.

Name:	us-gaap_CashAndSecuritiesSegregatedUnderFederalAndOtherRegulations
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Cash deposited in a special reserve account for the exclusive benefit of customers pursuant to SEC Regulations.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-SubTopic 210
-Topic 942
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481281/942-210-50-1