STOCKHOLDERS' EQUITY - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands			6 Months Ended
	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2016
Number of Stock Options Outstanding
Beginning balance (in shares)			107,515,554
Granted (in shares)			1,707,320
Exercised (in shares)			(4,225,876)
Forfeited (in shares)			(5,993,756)
Ending balance (in shares)	99,003,242	107,515,554	99,003,242
Weighted Average Exercise Price
Beginning balance (in USD per share)			$ 6.99
Granted (in USD per share)			13.54
Exercised (in USD per share)			1.91
Forfeited (in USD per share)			11.26
Ending balance (in USD per share)	$ 7.06	$ 6.99	$ 6.99
Options Vested and Expected to Vest
Options vested and expected to vest (in shares)	92,406,077
Options vested and expected to vest (in USD per share)	$ 6.79
Options Exercisable
Options exercisable (in shares)	94,552,296
Options exercisable (in USD per share)	$ 6.89
Additional Disclosures
Weighted average remaining contractual term, options outstanding	7 years 6 months 26 days	7 years 10 months 13 days
Weighted average remaining contractual term, options vested and expected to vest	6 years 10 months 17 days
Weighted average remaining contractual term, options exercisable	7 years 5 months 19 days
Aggregate intrinsic value, options outstanding	$ 307,645	$ 656,194
Aggregate intrinsic value, options vested and expected to vest	303,773
Aggregate intrinsic value, options exercisable	$ 307,645