SHAREHOLDERS' EQUITY AND SHARE-BASED COMPENSATION - Market prices necessary in order for the market performance options to begin to vest (Details)	Dec. 31, 2015 $ / shares shares
Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	47,500
Market-based options, Weighted average share price (in dollars per share) | $ / shares	$ 92.29
Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	55,875
Market-based options, Weighted average share price (in dollars per share) | $ / shares	$ 77.03
$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)	12,500
$180.01 - $190.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	25,875
Over $190.00
Market prices for market performance options to vest
Market-based options, Vesting price, low end of range (in dollars per share) | $ / shares	$ 190.00
Over $190.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	22,500
Over $190.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	30,000