INCENTIVE PLANS - Stock Options Outstanding (Details)	12 Months Ended
	Dec. 31, 2020 $ / shares shares
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number outstanding (in shares) | shares	166,650
Options outstanding, Weighted-average contractual life remaining	4 months 24 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 47.42
Options exercisable, Number exercisable (in shares) | shares	166,650
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 47.42
$41.54–$60.00
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price, low end of the range (in dollars per share)	41.54
Exercise price, high end of the range (in dollars per share)	$ 60.00
Number outstanding (in shares) | shares	166,650
Options outstanding, Weighted-average contractual life remaining	4 months 24 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 47.42
Options exercisable, Number exercisable (in shares) | shares	166,650
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 47.42