STATEMENTS OF CHANGES IN PREFERRED STOCK AND STOCKHOLDERS' Equity (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid In Capital Common Stock	Accumulated Deficit	Series 1 Preferred Stock - Mezzanine
Balance at Dec. 31, 2017	$ (96,806)	$ 143	$ 615,493	$ (712,442)	$ 143,992
Balance (in shares) at Dec. 31, 2017		142,658,037			119,644
Adjustment for implementation of ASU No. 2014-09, Revenue from Contracts with Customers	(8,131)			(8,131)
Stock-based compensation	5,370		5,370
Exercise of employee stock options	240		240
Exercise of employee stock options (in shares)		104,166
Cancelled restricted common stock (in shares)		(70,867)
Repurchase of restricted common stock	(1,275)	$ (1)	(1,274)
Repurchase of restricted common stock (Shares)		(311,566)
Preferred stock dividends			(10,582)		$ 10,436
Preferred stock dividends	(10,582)
Preferred stock dividends (in shares)					7,358
Net loss	(28,051)			(28,051)
Balance at Jun. 30, 2018	(139,235)	$ 142	609,247	(748,624)	$ 154,428
Balance (in shares) at Jun. 30, 2018		142,379,770			127,002
Balance at Mar. 31, 2018	(123,149)	$ 142	613,302	(736,593)	$ 149,039
Balance (in shares) at Mar. 31, 2018		142,398,936			123,268
Stock-based compensation	1,711		1,711
Exercise of employee stock options	240		240
Exercise of employee stock options (in shares)		104,166
Repurchase of restricted common stock	(544)		(544)
Repurchase of restricted common stock (Shares)		(123,332)
Preferred stock dividends			(5,462)		$ 5,389
Preferred stock dividends	(5,462)
Preferred stock dividends (in shares)					3,734
Net loss	(12,031)			(12,031)
Balance at Jun. 30, 2018	(139,235)	$ 142	609,247	(748,624)	$ 154,428
Balance (in shares) at Jun. 30, 2018		142,379,770			127,002
Balance at Dec. 31, 2018	85,564	$ 161	651,732	(566,329)
Balance (in shares) at Dec. 31, 2018		161,066,136
Stock-based compensation	3,255		3,255
Exercise of employee stock options	$ 600		600
Exercise of employee stock options (in shares)	332,416	258,068
Issuance of restricted common stock	$ 1,000	$ 1	999
Issuance of restricted common stock (in shares)		1,393,536
Cancelled restricted common stock (in shares)		(74,599)
Repurchase of restricted common stock	(370)		(370)
Repurchase of restricted common stock (Shares)		(165,178)
Net loss	(28,054)			(28,054)
Balance at Jun. 30, 2019	61,995	$ 162	656,216	(594,383)
Balance (in shares) at Jun. 30, 2019		162,477,963
Balance at Mar. 31, 2019	74,216	$ 162	653,817	(579,763)
Balance (in shares) at Mar. 31, 2019		162,287,161
Stock-based compensation	1,799		1,799
Exercise of employee stock options	600		600
Exercise of employee stock options (in shares)		258,068
Cancelled restricted common stock (in shares)		(67,266)
Net loss	(14,620)			(14,620)
Balance at Jun. 30, 2019	$ 61,995	$ 162	$ 656,216	$ (594,383)
Balance (in shares) at Jun. 30, 2019		162,477,963