STOCK-BASED COMPENSATION - Information for Stock Options Outstanding and Exercisable (Details) shares in Thousands	12 Months Ended
Dec. 31, 2018 $ / shares shares
Awards Outstanding
Options outstanding (shares) \| shares	33,158
Weighted Average Remaining Contractual Life in Years	6 years 10 months 24 days
Weighted-average exercise price (USD per share)	$ 3.42
Awards Exercisable
Options exercisable (shares) \| shares	17,612
Weighted Average Remaining Contractual Life in Years	6 years 1 month 6 days
Weighted-average exercise price (USD per share)	$ 2.78
$0.01 to $3.00
Awards Outstanding
Options outstanding (shares) \| shares	16,404
Weighted Average Remaining Contractual Life in Years	5 years 8 months 12 days
Weighted-average exercise price (USD per share)	$ 1.55
Awards Exercisable
Options exercisable (shares) \| shares	11,666
Weighted Average Remaining Contractual Life in Years	5 years 2 months 12 days
Weighted-average exercise price (USD per share)	$ 1.28
Exercise price range, lower limit (USD per share)	0.01
Exercise price range, upper limit (USD per share)	$ 3.00
$3.01 to $6.00
Awards Outstanding
Options outstanding (shares) \| shares	15,044
Weighted Average Remaining Contractual Life in Years	8 years 1 month 6 days
Weighted-average exercise price (USD per share)	$ 4.53
Awards Exercisable
Options exercisable (shares) \| shares	5,049
Weighted Average Remaining Contractual Life in Years	8 years 1 month 6 days
Weighted-average exercise price (USD per share)	$ 4.53
Exercise price range, lower limit (USD per share)	3.01
Exercise price range, upper limit (USD per share)	$ 6.00
$6.01 to $9.00
Awards Outstanding
Options outstanding (shares) \| shares	327
Weighted Average Remaining Contractual Life in Years	5 years 8 months 12 days
Weighted-average exercise price (USD per share)	$ 7.73
Awards Exercisable
Options exercisable (shares) \| shares	217
Weighted Average Remaining Contractual Life in Years	5 years 2 months 12 days
Weighted-average exercise price (USD per share)	$ 7.93
Exercise price range, lower limit (USD per share)	6.01
Exercise price range, upper limit (USD per share)	$ 9.00
$9.01 to $12.00
Awards Outstanding
Options outstanding (shares) \| shares	826
Weighted Average Remaining Contractual Life in Years	8 years 4 months 24 days
Weighted-average exercise price (USD per share)	$ 10.65
Awards Exercisable
Options exercisable (shares) \| shares	311
Weighted Average Remaining Contractual Life in Years	7 years 4 months 24 days
Weighted-average exercise price (USD per share)	$ 10.40
Exercise price range, lower limit (USD per share)	9.01
Exercise price range, upper limit (USD per share)	$ 12.00
$12.01 to $15.00
Awards Outstanding
Options outstanding (shares) \| shares	390
Weighted Average Remaining Contractual Life in Years	7 years 3 months 18 days
Weighted-average exercise price (USD per share)	$ 13.01
Awards Exercisable
Options exercisable (shares) \| shares	202
Weighted Average Remaining Contractual Life in Years	5 years 10 months 24 days
Weighted-average exercise price (USD per share)	$ 13.25
Exercise price range, lower limit (USD per share)	12.01
Exercise price range, upper limit (USD per share)	$ 15.00
$15.01 to $18.00
Awards Outstanding
Options outstanding (shares) \| shares	1
Weighted Average Remaining Contractual Life in Years	3 years 2 months 12 days
Weighted-average exercise price (USD per share)	$ 15.47
Awards Exercisable
Options exercisable (shares) \| shares	1
Weighted Average Remaining Contractual Life in Years	3 years 2 months 12 days
Weighted-average exercise price (USD per share)	$ 15.47
Exercise price range, lower limit (USD per share)	15.01
Exercise price range, upper limit (USD per share)	$ 18.00
$18.01 to $21.00
Awards Outstanding
Options outstanding (shares) \| shares	115
Weighted Average Remaining Contractual Life in Years	4 years 2 months 12 days
Weighted-average exercise price (USD per share)	$ 19.88
Awards Exercisable
Options exercisable (shares) \| shares	115
Weighted Average Remaining Contractual Life in Years	4 years 2 months 12 days
Weighted-average exercise price (USD per share)	$ 19.88
Exercise price range, lower limit (USD per share)	18.01
Exercise price range, upper limit (USD per share)	$ 21.00
$21.01 to $24.00
Awards Outstanding
Options outstanding (shares) \| shares	51
Weighted Average Remaining Contractual Life in Years	3 years 10 months 24 days
Weighted-average exercise price (USD per share)	$ 22.66
Awards Exercisable
Options exercisable (shares) \| shares	51
Weighted Average Remaining Contractual Life in Years	3 years 10 months 24 days
Weighted-average exercise price (USD per share)	$ 22.66
Exercise price range, lower limit (USD per share)	21.01
Exercise price range, upper limit (USD per share)	$ 24.00

Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable [Abstract]

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Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding [Abstract]

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The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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The number of shares reserved for issuance pertaining to the outstanding exercisable stock options as of the balance sheet date in the customized range of exercise prices for which the market and performance vesting condition has been satisfied.

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The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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Weighted average exercise price as of the balance sheet date for those equity-based payment arrangements exercisable and outstanding.

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Weighted average remaining contractual term of exercisable stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The weighted average price as of the balance sheet date at which grantees could acquire the underlying shares with respect to all outstanding stock options which are in the customized range of exercise prices.

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Weighted average remaining contractual term of outstanding stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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