STOCK-BASED EMPLOYEE COMPENSATION (Tables)

3 Months Ended

Mar. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Activity of unvested restricted stock units and performance share units

Restricted Stock Units and Performance Share Units

The following table summarizes the activity of restricted stock units and performance share units ("share-based awards") during the three months ended March 31, 2018: 

Share-Based Awards	Shares		Weighted-Average Grant Date Fair Value
Unvested at December 31, 2017	524,696			$	1,431.88
Granted	146,112			$	2,033.79
Vested	(146,766	)		$	1,271.70
Performance Shares Adjustment	6,487			$	1,654.15
Forfeited/Canceled	(6,718	)		$	1,594.90
Unvested at March 31, 2018	523,811			$	1,645.32

Schedule of share-based compensation, stock options, activity

Stock Options

All outstanding employee stock options were assumed in acquisitions. The following table summarizes the activity for stock options during the three months ended March 31, 2018: 

Employee Stock Options	Number of Shares		Weighted-Average Exercise Price			Aggregate  Intrinsic Value (in thousands)			Weighted-Average Remaining Contractual Term (in years)
Balance, December 31, 2017	30,675			$	401.61		$	40,986	3.9
Exercised	(2,416	)		$	477.21
Forfeited	(11	)		$	66.98
Balance, March 31, 2018	28,248			$	395.35		$	47,599	3.6
Vested and exercisable as of March 31, 2018	28,160			$	403.59		$	47,509	3.6
Vested and exercisable as of March 31, 2018 and expected to vest thereafter	28,248			$	395.35		$	47,599	3.6