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STOCKHOLDERS' EQUITY - Dividends (Details) - USD ($) $ / shares in Units, $ in Millions										1 Months Ended		2 Months Ended	3 Months Ended	6 Months Ended
	Jun. 03, 2021	Jun. 01, 2021	Apr. 27, 2021	Feb. 01, 2021	Jan. 27, 2021	Jan. 25, 2021	Dec. 14, 2020	Dec. 11, 2020	Feb. 26, 2020	Jun. 30, 2021	Dec. 31, 2020	May 31, 2021	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
STOCKHOLDERS' EQUITY
Other financing costs														$ 19.3	$ 9.3
Dividends
Cash dividend declared (in dollars per share)									$ 0.03
Dividends declared									$ 3.2
Dividends and dividend equivalents															$ 4.3
Mudrick Capital Management LP [Member]
STOCKHOLDERS' EQUITY
Gross proceeds														$ 230.4
At-the-market equity offerings
STOCKHOLDERS' EQUITY
Number of shares issued	11,550,000		43,000,000.0			50,000,000.0		137,070,000.00						241,620,000
Gross proceeds	$ 587.4		$ 427.5			$ 244.3		$ 352.6						$ 1,611.8
Class A common stock
STOCKHOLDERS' EQUITY
Number of shares authorized										524,173,073	524,173,073			524,173,073
Sell price per share										$ 0.01	$ 0.01			$ 0.01
Gross proceeds														$ 1,570.8
Consideration received for conversion				46,103,784
Dividends
Cash dividend declared (in dollars per share)													$ 0.03
Class A common stock \| Mudrick Capital Management LP [Member]
STOCKHOLDERS' EQUITY
Number of shares issued							21,978,022
Consideration received for commitment fee							8,241,758
Class A common stock \| Equity Distribution Agreement [Member]
STOCKHOLDERS' EQUITY
Number of shares authorized								178,000,000.0		241,600,000				241,600,000
Sell price per share										$ 0.01				$ 0.01
Number of shares issued											40,930,000			137,070,000.00
Gross proceeds														$ 1,611.8
Sales agents fees paid														40.3
Other financing costs														$ 0.7
Class A common stock \| At-the-market equity offerings
STOCKHOLDERS' EQUITY
Number of shares issued										11,550,000		43,000,000.0
Gross proceeds										$ 587.4		$ 427.5
Sales agents fees paid										14.7		$ 10.7
Other financing costs										$ 0.3
Reissuance of treasury stock shares														3,700,000
Reissuance of treasury stock														$ 43.0
Amount reclassified into additional paid-in capital														37.1
Amount reclassified into retained earnings														$ 19.3
Class B common stock
STOCKHOLDERS' EQUITY
Number of shares authorized										0	51,769,784			0
Sell price per share										$ 0.01	$ 0.01			$ 0.01
Dividends
Cash dividend declared (in dollars per share)													$ 0.03
Class B common stock \| Wanda
STOCKHOLDERS' EQUITY
Shares forfeited					5,666,000
Second Lien Notes due 2026 \| Mudrick Capital Management LP [Member]
STOCKHOLDERS' EQUITY
Consideration received for conversion							13,736,264
Second Lien Notes due 2026 \| Private Placement \| Mudrick Capital Management LP [Member]
STOCKHOLDERS' EQUITY
Gross proceeds		$ 230.5
Other financing costs		$ 0.1
Second Lien Notes due 2026 \| Class A common stock \| Private Placement \| Mudrick Capital Management LP [Member]
STOCKHOLDERS' EQUITY
Number of shares issued		8,500,000