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STOCKHOLDERS' EQUITY - Narrative (Details) $ / shares in Units, $ in Millions				12 Months Ended
	Oct. 30, 2020	Mar. 05, 2020 shares	Feb. 26, 2020 shares	Dec. 31, 2020 USD ($) item $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 shares	Dec. 31, 2016 shares	Feb. 27, 2020 shares
Additional Public Offering
Class A common stock issuance \| $				$ 264.7
Treasury Stock
Share repurchase program				200,000,000.0
Stock repurchase program period				3 years
Equity disclosures
Total estimated unrecognized compensation cost related to nonvested stock-based compensation arrangements \| $				$ 15.2
Weighted average period recognized				1 year 6 months
Stock-based compensation \| $				$ 25.4	$ 4.4	$ 14.9
Number of days for settlement				30 days
Requisite service period	3 years
Additional Paid-in Capital
Additional Public Offering
Class A common stock issuance \| $				$ 263.8
Equity disclosures
Stock-based compensation \| $				25.4	4.4	14.9
General and administrative: other
Equity disclosures
Stock-based compensation expense \| $				$ 25.4	$ 4.4	$ 14.9
2.95% Senior Secured Convertible Notes due 2024
Equity disclosures
Price per share (in dollars per share) \| $ / shares				$ 2.12
Members of management and executive officers \| Performance Vesting
Equity disclosures
Period of cumulative adjusted EBITDA, diluted earnings per share, and net profit results to meet the performance target condition					3 years
Special Performance Stock Unit
Equity disclosures
Requisite service period				6 years 4 months 24 days
Special Performance Stock Unit \| General and administrative: other
Equity disclosures
Stock-based compensation expense \| $				$ 14.0
RSU and PSU Units \| Minimum
Equity disclosures
Price per share (in dollars per share) \| $ / shares				$ 2.36	$ 2.36	$ 2.36
RSU and PSU Units \| Maximum
Equity disclosures
Price per share (in dollars per share) \| $ / shares				$ 15.65
Performance Vesting
Equity disclosures
Stock-based compensation expense \| $					$ 5.8
Percentage of awards forfeited					100.00%
Percentage of performance targets and vesting level	90.00%
Performance Vesting \| General and administrative: other
Equity disclosures
Stock-based compensation expense \| $				$ 1.2	$ (5.8)	$ 5.8
Performance Vesting \| Members of management and executive officers
Equity disclosures
Restricted stock unit granted (in shares)				1,436,297	730,167	653,669
Number of days from the termination of service for settlement of fully vested units				30 days
Period of cumulative adjusted EBITDA, diluted earnings per share, and net profit results to meet the performance target condition				3 years	3 years
Awards to be granted if target not achieved (in shares)				0
Performance Vesting \| Members of management and executive officers \| Minimum
Equity disclosures
PSUs vesting as a percentage of performance target				80.00%
Percentage of performance target				50.00%	30.00%
Performance Vesting \| Members of management and executive officers \| Maximum
Equity disclosures
PSUs vesting as a percentage of performance target				120.00%
Percentage of performance target				200.00%	200.00%
2013 Equity Incentive Plan \| Stock options
Equity disclosures
Number of shares authorized				15,000,000
Number of shares remaining available for grant				8,520,193
2013 Equity Incentive Plan \| Stock options \| Board of Director
Equity disclosures
Stock-based compensation expense \| $				$ 0.5	$ 0.5	$ 0.5
2013 Equity Incentive Plan \| Performance Stock Unit Transition Award \| Executive officers
Equity disclosures
Restricted stock unit granted (in shares)					300,000
2013 Equity Incentive Plan \| Special Performance Stock Unit \| Executive officers
Equity disclosures
Restricted stock unit granted (in shares)		3,570,000	3,570,000
Vesting period (in years)				10 years
Number of days for settlement				20 days
Requisite service period				3 years
2013 Equity Incentive Plan \| Restricted stock unit \| Members of management and executive officers
Equity disclosures
Number of shares to be received for each unit				1
2013 Equity Incentive Plan \| Restricted stock unit \| Members of management
Equity disclosures
Number of days from the termination of service for settlement of fully vested units				30 days
Percentage of options that will vest on each of the anniversaries from the date of grant				33.00%	33.00%	33.00%
Vesting period (in years)				3 years	3 years	3 years
2013 Equity Incentive Plan \| Restricted stock unit \| Executive officers
Equity disclosures
Restricted stock unit granted (in shares)							129,214	135,981
Percentage of options that will vest on each of the anniversaries from the date of grant				33.00%	33.00%	33.00%
Vesting period (in years)				3 years
Number of days for settlement				30 days
2013 Equity Incentive Plan \| 2020 RSU awards \| Members of management
Equity disclosures
Restricted stock unit granted (in shares)				1,511,297
Recorded stock-based compensation expense \| $				$ 8.7
2013 Equity Incentive Plan \| 2019 RSU awards \| Members of management
Equity disclosures
Restricted stock unit granted (in shares)					730,167
Recorded stock-based compensation expense \| $					$ 8.2
2013 Equity Incentive Plan \| 2019 RSU awards \| Executive officers
Equity disclosures
Stock-based compensation expense \| $					1.4
2013 Equity Incentive Plan \| 2018 RSU awards \| Members of management
Equity disclosures
Restricted stock unit granted (in shares)						656,576
Recorded stock-based compensation expense \| $						$ 6.2
2013 Equity Incentive Plan \| 2018 RSU awards \| Executive officers
Equity disclosures
Stock-based compensation expense \| $						$ 2.4
2013 Equity Incentive Plan \| 2019 RSU executive \| Members of management
Equity disclosures
Stock-based compensation expense \| $				$ 1.0	$ 0.1
2013 Equity Incentive Plan \| 2019 RSU executive \| Executive officers
Equity disclosures
Restricted stock unit granted (in shares)				200,000
Vesting period (in years)				3 years
Number of days for settlement				30 days
2013 Equity Incentive Plan \| Performance Vesting \| Members of management and executive officers
Equity disclosures
Awards to be granted upon achieving 100% of performance target (in shares)				1,436,297
Class A common stock
Common Stock Rights and Privileges
Number of votes per share \| item				1
Additional Public Offering
Gross proceeds \| $				$ 264.7
Treasury Stock
Share repurchase program									200,000,000.0
Class A common stock \| 2013 Equity Incentive Plan \| Stock options \| Board of Director
Equity disclosures
Shares granted				77,090	32,464	28,055
Class B common stock
Common Stock Rights and Privileges
Number of votes per share \| item				3
Number of shares to be issued on conversion of each common stock at option of holder				1
Number of shares to be issued on automatic conversion of each common stock				1