Number of new stock issued during the period.

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Name:	us-gaap_StockIssuedDuringPeriodSharesNewIssues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

CONVERTIBLE SENIOR NOTES AND CALL OPTIONS - Convertible notes 2024 (Details) - USD ($) $ in Millions		1 Months Ended		12 Months Ended
	Jan. 22, 2014	May 31, 2019	Feb. 28, 2018	Dec. 31, 2020
Debt Instrument [Line Items]
Stock Issued During Period, Shares, New Issues		18,687,500	16,560,000	5,976,272
2024 Convertible Notes
Debt Instrument [Line Items]
Proceeds from Issuance of Debt				$ 30
American Depositary Shares
Debt Instrument [Line Items]
Stock Issued During Period, Shares, New Issues	3,750,000	4,671,875	4,140,000	1,494,068