EQUITY COMPENSATION - RSUs (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
RSU With Performance Measures
Nonvested Restricted Share Units
Beginning balance (in shares)	197,250
Granted (in shares)	175,991
Forfeited (in shares)	(25,277)
Ending balance (in shares)	347,964	197,250
Grant Date Fair Value*
Weighted average beginning balance (in dollars per share)	$ 37.87
Weighted average granted (in dollars per share)	87.98	$ 37.87
Weighted average, forfeited (in dollars per share)	60.55
Weighted average ending balance (in dollars per share)	$ 61.57	$ 37.87
Remaining weighted-average contractual term (in years)	1 year 8 months 12 days
Total unrecognized compensation expense,	$ 17.5
Vested (in shares)	0	0
RSUs
Nonvested Restricted Share Units
Beginning balance (in shares)	233,350
Granted (in shares)	59,539
Forfeited (in shares)	(11,611)
Ending balance (in shares)	160,742	233,350
Grant Date Fair Value*
Weighted average beginning balance (in dollars per share)	$ 54.16
Weighted average granted (in dollars per share)	68.92	$ 54.47	$ 52.16
Weighted average, vested (in dollars per share)	53.94
Weighted average, forfeited (in dollars per share)	59.27
Weighted average ending balance (in dollars per share)	$ 59.42	$ 54.16
Remaining weighted-average contractual term (in years)	1 year 3 months 18 days
Total unrecognized compensation expense,	$ 3.5
Vested (in shares)	120,536
Total fair value of shares	$ 6.5	$ 2.6	$ 16.0