STOCK-BASED COMPENSATION - Summary of stock options and stock options with market conditions (Details)	6 Months Ended
	Jun. 30, 2021 USD ($) $ / shares shares
Stock options, Grant Date Fair Value Valuation
Share price (in dollars per share) | $ / shares	$ 211.88
Grant date fair value (in dollars per share) | $ / shares	$ 130.25
Option
Stock options, Shares
Outstanding at the beginning of the period (in shares) | shares	924,710
Granted (in shares) | shares	69,258
Exercised (in shares) | shares	(156,113)
Forfeited (in shares) | shares	(4,727)
Expired (in shares) | shares	(35)
Outstanding at the end of the period (in shares) | shares	833,093
Options exercisable at the end of the period (in shares) | shares	543,666
Stock options, Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 111.82
Granted (in dollars per share) | $ / shares	243.71
Exercised (in dollars per share) | $ / shares	7.17
Forfeited (in dollars per share) | $ / shares	263.72
Expired (in dollars per share) | $ / shares	371.25
Outstanding at the end of the period (in dollars per share) | $ / shares	141.52
Options exercisable at the end of the period (in dollars per share) | $ / shares	$ 71.06
Stock options, Weighted Average Remaining Contractual Term
Outstanding at the end of the period	5 years 2 months 12 days
Options exercisable at the end of the period	3 years 2 months 12 days
Stock options, Aggregate Intrinsic Value
Outstanding at the end of the period | $	$ 82,110,000
Options exercisable at the end of the period | $	$ 82,039,000
Stock options, Grant Date Fair Value Valuation
Expected dividend rate	0.00%
Expected dividends | $	$ 0
Option | Vesting period one
Stock options, Grant Date Fair Value Valuation
Vesting period	1 year
Option | Vesting period two
Stock options, Grant Date Fair Value Valuation
Vesting period	3 years
Option | Minimum
Stock options, Grant Date Fair Value Valuation
Expected term	5 years
Risk-free interest rate	0.59%
Expected volatility rate	53.00%
Option | Maximum
Stock options, Grant Date Fair Value Valuation
Expected term	6 years
Risk-free interest rate	1.07%
Expected volatility rate	59.00%
Market options
Stock options, Shares
Outstanding at the beginning of the period (in shares) | shares	700,209
Granted (in shares) | shares	0
Exercised (in shares) | shares	0
Forfeited (in shares) | shares	0
Expired (in shares) | shares	0
Outstanding at the end of the period (in shares) | shares	700,209
Options exercisable at the end of the period (in shares) | shares	0
Stock options, Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 236.01
Granted (in dollars per share) | $ / shares	0
Exercised (in dollars per share) | $ / shares	0
Forfeited (in dollars per share) | $ / shares	0
Expired (in dollars per share) | $ / shares	0
Outstanding at the end of the period (in dollars per share) | $ / shares	236.01
Options exercisable at the end of the period (in dollars per share) | $ / shares	$ 0
Stock options, Weighted Average Remaining Contractual Term
Outstanding at the end of the period	7 years 3 months
Options exercisable at the end of the period	0 years
Stock options, Aggregate Intrinsic Value
Outstanding at the end of the period | $	$ 11,308,000
Options exercisable at the end of the period | $	$ 0
Stock options, Grant Date Fair Value Valuation
Maximum number of shared to be earned | shares	1,169,349
Percentage of target number of shares	167.00%
Performance awards earned (in shares) | shares	481,669