SHAREHOLDERS' EQUITY AND SHARE-BASED COMPENSATION - Market-based options vesting prices (Details)	Dec. 31, 2019 $ / shares shares
Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	97,736
Market-based options, weighted average share price (in dollars per share) | $ / shares	$ 51.06
Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	74,507
Market-based options, weighted average share price (in dollars per share) | $ / shares	$ 48.53
$40.01 — $50.00
Market prices for market performance options to vest
Market-based options, vesting price, low end of range (in dollars per share) | $ / shares	40.01
Market-based options, vesting price, high end of range (in dollars per share) | $ / shares	$ 50.00
$40.01 — $50.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	3,125
$40.01 — $50.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	0
$50.01 — $60.00
Market prices for market performance options to vest
Market-based options, vesting price, low end of range (in dollars per share) | $ / shares	$ 50.01
Market-based options, vesting price, high end of range (in dollars per share) | $ / shares	$ 60.00
$50.01 — $60.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	44,796
$50.01 — $60.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	5,327
$60.01 — $70.00
Market prices for market performance options to vest
Market-based options, vesting price, low end of range (in dollars per share) | $ / shares	$ 60.01
Market-based options, vesting price, high end of range (in dollars per share) | $ / shares	$ 70.00
$60.01 — $70.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	14,815
$60.01 — $70.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	6,250
$70.01 — $80.00
Market prices for market performance options to vest
Market-based options, vesting price, low end of range (in dollars per share) | $ / shares	$ 70.01
Market-based options, vesting price, high end of range (in dollars per share) | $ / shares	$ 80.00
$70.01 — $80.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	0
$70.01 — $80.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	11,500
$80.01 — $90.00
Market prices for market performance options to vest
Market-based options, vesting price, low end of range (in dollars per share) | $ / shares	$ 80.01
Market-based options, vesting price, high end of range (in dollars per share) | $ / shares	$ 90.00
$80.01 — $90.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	0
$80.01 — $90.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	11,397
$90.01 — $100.00
Market prices for market performance options to vest
Market-based options, vesting price, low end of range (in dollars per share) | $ / shares	$ 90.01
Market-based options, vesting price, high end of range (in dollars per share) | $ / shares	$ 100.00
$90.01 — $100.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	0
$90.01 — $100.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	6,908
$100.01 — $110.00
Market prices for market performance options to vest
Market-based options, vesting price, low end of range (in dollars per share) | $ / shares	$ 100.01
Market-based options, vesting price, high end of range (in dollars per share) | $ / shares	$ 110.00
$100.01 — $110.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	0
$100.01 — $110.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	1,000
$170.01 — $180.00
Market prices for market performance options to vest
Market-based options, vesting price, low end of range (in dollars per share) | $ / shares	$ 170.01
Market-based options, vesting price, high end of range (in dollars per share) | $ / shares	$ 180.00
$170.01 — $180.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	12,500
$170.01 — $180.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	0
$180.01 — $190.00
Market prices for market performance options to vest
Market-based options, vesting price, low end of range (in dollars per share) | $ / shares	$ 180.01
Market-based options, vesting price, high end of range (in dollars per share) | $ / shares	$ 190.00
$180.01 — $190.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	7,500
$180.01 — $190.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	14,625
Over $190.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	15,000
Over $190.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	17,500