STOCK-BASED COMPENSATION (Tables)

6 Months Ended

Jun. 30, 2018

STOCK-BASED COMPENSATION

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

	Three-Months Ended June 30,		Six-Months Ended June 30,
	2018	2017	2018	2017
Dividend yield	0.0%	0.0%	0.0%	0.0%
Expected volatility	34.9%	36.5%	34.9%	36.6%
Risk-free interest rate	2.7%	1.8%	2.8%	2.1%
Expected term	6.1 years	6.1 years	6.1 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
Granted 04/01/18 - 06/30/18	360	$	51.72
Exercised	(814)	$	16.73
Cancelled or forfeited	(216)	$	42.60
Outstanding at June 30, 2018	19,764	$	34.26	6.2	$	459,527
Vested and expected to vest in the
future at June 30, 2018	18,673	$	33.32	6.1	$	451,327
Exercisable at June 30, 2018	10,639	$	22.40	4.5	$	371,252

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
Granted 04/01/18- 06/30/18	48	$	52.31
Vested	(262)	$	45.36
Forfeited/cancelled	(6)	$	32.17
Non-vested at June 30, 2018	531	$	51.45