QUARTERLY FINANCIAL INFORMATION (UNAUDITED) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 22,093	$ 23,441	$ 23,994	$ 20,536	$ 20,994	$ 22,549	$ 19,835	$ 19,333	$ 19,062	$ 20,537	$ 19,981	$ 16,738	$ 90,064	$ 82,711	$ 76,318
Net loss	$ 92,015	$ 129,390	$ (433,730)	$ (250,541)	$ (234,797)	$ (204,969)	$ (126,272)	$ (25,078)	$ (18,952)	$ (41,188)	$ (27,533)	$ (24,525)	$ (462,866)	$ (591,116)	$ (112,198)
Basic loss per common share (USD per share)	$ 0.09	$ 0.13	$ (0.48)	$ (0.29)	$ (0.36)	$ (0.30)	$ (0.25)	$ (0.05)	$ (0.05)	$ (0.10)	$ (0.07)	$ (0.07)	$ (0.50)	$ (0.96)	$ (0.29)
Diluted loss per common share (USD per share)	$ 0.08	$ 0.11	$ (0.48)	$ (0.29)	$ (0.36)	$ (0.30)	$ (0.25)	$ (0.05)	$ (0.05)	$ (0.10)	$ (0.07)	$ (0.07)	$ (0.50)	$ (0.96)	$ (0.29)
Shares used in basic per share calculations	993,427	987,668	904,994	849,321	779,483	673,546	496,169	472,187	424,180	392,344	379,433	357,418	934,356	614,959	388,453
Shares used in diluted per share calculations	1,192,263	1,189,190	904,994	849,321	779,483	673,546	496,169	472,187	424,180	392,344	379,433	357,418	934,356	614,959	388,453