STOCK-BASED COMPENSATION (Tables)

3 Months Ended

Mar. 31, 2018

STOCK-BASED COMPENSATION

Schedule of weighted-average assumptions used to estimate the fair value of options granted

	Three-Months Ended March 31,
	2018	2017
Dividend yield	0.0%	0.0%
Expected volatility	34.9%	36.6%
Risk-free interest rate	2.8%	2.1%
Expected term	6.0 years	6.1 years

Summary of Company's activities with respect to its stock option plans

Options	Number of Shares (In thousands)	Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (In years)	Aggregate Intrinsic Value
Outstanding at January 1, 2018	17,819	$	29.62	6.1	$	600,032
Granted 01/01/18 - 03/31/18	2,615	$	58.76
Exercised	(415)	$	15.68
Cancelled or forfeited	(192)	$	43.02
Outstanding at March 31, 2018	19,827	$	33.62	6.4	$	472,160
Vested and expected to vest in the
future at March 31, 2018	18,689	$	32.62	6.3	$	463,173
Exercisable at March 31, 2018	10,834	$	21.99	4.7	$	381,567

Summary of Company's activities with respect to non-vested restricted stock units

	Number of Shares (in thousands)	Weighted Average Grant-Date Fair Value
Non-vested at January 1, 2018	530	$	45.09
Granted 01/01/18- 03/31/18	221	$	58.75
Vested	(255)	$	45.62
Forfeited/cancelled	(6)	$	32.17
Non-vested at March 31, 2018	490	$	51.15