INCOME TAXES - Movement of the valuation allowance (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Movement of allowances
Beginning of the year	$ 70,627
End of the year	50,118	$ 70,627
Allowance
Movement of allowances
Beginning of the year	70,627	76,522	$ 65,399
Additions (Reversals)	(21,585)	(6,156)	11,051
Foreign exchange effect	1,076	261	72
End of the year	$ 50,118	$ 70,627	$ 76,522

Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs which have been charged to costs and expenses net of the total of recoveries of amounts due the Entity that had previously been written off as uncollectible using allowances (the valuation accounts that are netted against the cost of an asset to value it at its carrying value) and total of reestablishments of reserves (liabilities established to represent expected future costs) that had previously been utilized.

No definition available.

Name:	csiq_ValuationAllowancesAndReservesChargedToCostAndExpenseAndRecoveriesNet
Namespace Prefix:	csiq_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration