Quarterly Financial Data (Selected Quarterly Financial Data) (Details) - USD ($)	3 Months Ended								6 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2014	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2014
Revenue	$ 128,000	$ 143,000	$ 102,000	$ 102,000	$ 101,000	$ 103,000	$ 101,000	$ 104,000			$ 475,000	$ 409,000
Total operating expenses	3,068,000	2,571,000	2,694,000	2,369,000	2,698,000	5,334,000	3,849,000	2,638,000			10,702,000	14,519,000
Loss from operations	(2,940,000)	(2,428,000)	(2,592,000)	(2,267,000)	(2,597,000)	(5,231,000)	(3,748,000)	(2,534,000)			(10,227,000)	(14,110,000)
Other income (expense), net	636,000	7,867,000	13,361,000	(12,226,000)							9,638,000	37,219,000
Other income					1,933,000	26,438,000	17,621,000
Other expense								(8,773,000)			(302,000)
Income tax benefit	73,000										73,000
Net (loss) income	(2,231,000)	5,439,000	10,769,000	(14,493,000)	(664,000)	21,207,000	13,873,000	(11,307,000)			(516,000)	23,109,000
Accretion of Series B redeemable convertible preferred stock	(949,000)	(7,163,000)	(1,828,000)	(338,000)	(330,000)	(323,000)	(318,000)	(314,000)			(10,278,000)	(1,285,000)
Net (loss) income attributable to common stockholders	$ (3,180,000)	$ (1,724,000)	$ 7,225,000	$ (14,831,000)	$ (994,000)	$ 14,493,000	$ 9,389,000	$ (11,621,000)	$ 1,732,000	$ 16,115,000	$ (10,794,000)	$ 15,757,000
Net (loss) income per share of common stock - basic	$ (0.54)	$ (0.30)	$ 1.27	$ (3.49)	$ (0.25)	$ 3.87	$ 2.56	$ (3.18)	$ 0.47	$ 4.37	$ (1.99)	$ 4.21
Net (loss) income per share of common stock - diluted	$ (0.54)	$ (0.30)	$ (0.33)	$ (3.49)	$ (0.44)	$ (0.86)	$ (0.63)	$ (3.18)	$ (1.06)	$ (1.96)	$ (1.99)	$ (2.33)
Scenario, Previously Reported [Member]
Net (loss) income attributable to common stockholders			$ 8,941,000			$ 20,884,000	$ 13,555,000		$ 1,934,000	$ 22,818,000		$ 21,824,000
Net (loss) income per share of common stock - basic			$ 1.58			$ 5.58	$ 3.69		$ 0.53	$ 6.19		$ 5.82
Net (loss) income per share of common stock - diluted			$ 1.17			$ 3.30	$ 2.09		$ 0.30	$ 3.53		$ 3.37