QUARTERLY FINANCIAL DATA (UNAUDITED) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information

The following information has been derived from unaudited consolidated financial statements that, in the opinion of management, include all recurring adjustments necessary for a fair statement of such information.

	Three Months Ended
	March 31, 2017			June 30, 2017			September 30, 2017			December 31, 2017
	(In thousands, except per share data)
Revenues	$	18,960		$	15,932		$	17,096		$	37,924
Operating expenses		125,471			136,406			142,896		$	185,227
Net loss	$	(107,290	)	$	(118,420	)	$	(122,937	)	$	(142,227	)
Net loss per common share — basic and diluted	$	(1.25	)	$	(1.34	)	$	(1.34	)	$	(1.48	)
Weighted-average common shares — basic and diluted		86,027			88,098			91,828			96,139

	Three Months Ended
	March 31, 2016			June 30, 2016			September 30, 2016			December 31, 2016
	(In thousands, except per share data)
Revenues	$	7,345		$	8,709		$	13,651		$	17,454
Operating expenses		117,373			101,159			120,327			132,887
Net loss	$	(102,974	)	$	(90,129	)	$	(104,071	)	$	(112,934	)
Net loss per common share — basic and diluted	$	(1.21	)	$	(1.05	)	$	(1.21	)	$	(1.32	)
Weighted-average common shares — basic and diluted		85,277			85,545			85,716			85,843