STOCK-BASED COMPENSATION, Stock-Based Compensation - Additional Information (Details) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended			6 Months Ended				6 Months Ended		0 Months Ended	6 Months Ended	0 Months Ended
	Jun. 30, 2014	Jun. 30, 2014 Restricted Stock	Dec. 31, 2013 Restricted Stock	Jun. 30, 2014 Stock Options	Jun. 30, 2014 Service-Based Awards	Jun. 30, 2014 Performance-Based Awards	Dec. 31, 2013 Performance-Based Awards	Jun. 30, 2014 2012 Plan Restricted Stock Units (RSUs)	Jun. 30, 2014 2012 Plan Stock Options	Jan. 11, 2012 2012 Directors Plan	Jun. 30, 2014 2012 Directors Plan Restricted Stock	Mar. 31, 2014 2006 Plan Stock Options	Jun. 30, 2014 2006 Plan Stock Options Maximum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Granted, Fair Value									$ 31,989
Shares authorized to be reserved for issuance (in shares)										600,000
2012 Directors Plan expiration period										10 years
Common stock shares available for issuance (in shares)									6,418,535
Common stock shares subject to outstanding awards that expire or terminate that are available for awards to be granted (in shares)													2,101,091
Options issued expiration period												10 years
Stock options issued, grant date fair value					14,590
Stock options vesting term									4 years
Underlying options, in shares	6,085
Underlying service-based awards, unvested and outstanding (in shares)		685,901	344,928		556,240	329,818	0
Underlying options, value at grant date					18,779
Unrecognized compensation cost, net of forfeitures	48,936
Weighted average remaining contractual term, exercisable	5 years 7 months
Weighted average remaining contractual term, outstanding	9 years 1 month
Non-vested common stock shares issued (in shares)											5,136
Restricted stock issued, value at grant date											225
Total unrecognized compensation cost related to non-vested share-based compensation awards granted						13,780		1,713			332
Total unrecognized compensation cost related to non-vested share-based compensation awards granted, period for recognition				2 years 2 months	1 year 10 months	2 years		2 years 5 months			1 year 3 months
Deferred compensation, shares issued								66,000
Deferred compensation arrangement, fair value of shares issued								$ 1,908
Stock options issued (in shares)		425,254			354,118	376,966