STOCK-BASED COMPENSATION - Fair Value Assumptions (Details) - Stock options - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Weighted-average assumptions used to estimate the fair value of options granted
Dividend yield (as a percent)	0.00%	0.00%
Expected volatility (as a percent)	36.20%	37.10%
Risk-free interest rate (as a percent)	1.50%	1.60%
Expected term	5 years 8 months 12 days	5 years 9 months 18 days
Stock Options, Number of Shares
Balance at the beginning of the period (in shares)	6,590
Granted (in shares)	961
Exercised (in shares)	(110)
Cancelled or forfeited (in shares)	(8)
Balance at the end of the period (in shares)	7,433		6,590
Vested and expected to vest in the future at the end of the period (in shares)	6,969
Exercisable at the end of the period (in shares)	4,257
Stock options, Weighted-Average Exercise Price Per Share
Balance at the beginning of the period (in dollars per share)	$ 50.85
Granted (in dollars per share)	132.06
Exercised (in dollars per share)	37.18
Cancelled or forfeited (in dollars per share)	93.05
Balance at the end of the period (in dollars per share)	61.50		$ 50.85
Vested and expected to vest in the future at the end of the period (in dollars per share)	57.97
Exercisable at the end of the period (in dollars per share)	$ 30.38
Weighted-Average Remaining Contractual Term
Balance at the beginning of the period	5 years 8 months 12 days		5 years 7 months 6 days
Balance at the end of the period	5 years 8 months 12 days		5 years 7 months 6 days
Vested and expected to vest in the future at the end of the period	5 years 6 months
Exercisable at the end of the period	4 years
Aggregate Intrinsic Value
Balance at the beginning of the period	$ 646,497
Balance at the end of the period	536,196		$ 646,497
Vested and expected to vest in the future at the end of the period	527,253
Exercisable at the end of the period	$ 438,805