SIGNIFICANT ACCOUNTING POLICIES - EPS (Details)	12 Months Ended
Dec. 31, 2020 item
Common Stock
Earnings per share:
Voting right per share (in votes per share)	1
Class B Common Stock
Earnings per share:
Voting right per share (in votes per share)	10

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_ClassOfStockLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration