Senior Convertible Notes - Narrative (Details) - USD ($)			1 Months Ended	2 Months Ended	3 Months Ended								12 Months Ended
	Mar. 18, 2016	Nov. 03, 2014	Nov. 30, 2016	Dec. 31, 2014	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Nov. 01, 2014
Debt Instrument [Line Items]
Accrued interest payable					$ 294,000				$ 1,988,000				$ 294,000	$ 1,988,000
Amortization of deferred debt costs													6,921,000	4,566,000	$ 411,000
Debt conversion amount													137,941,000	40,989,000	0
Common stock issued for interest on Notes													2,445,000	0	0
Debt conversion expense					14,543,000	$ 0	$ 0	$ 25,615,000					$ 40,158,000	0	0
Common Shares
Debt Instrument [Line Items]
Debt conversion expense (in shares)	9,600,000												12,161,671
Convertible Senior Notes Due 2019
Debt Instrument [Line Items]
Aggregate principal amount		$ 200,000,000		$ 200,000,000	23,500,000				159,000,000				$ 23,500,000	159,000,000	200,000,000
Interest rate		7.50%
Additional aggregate principal amount pertaining to the over-allotment option granted		$ 25,000,000
Net proceeds from offering		$ 187,300,000
Accrued interest expense			$ 2,000,000										6,700,000	12,900,000
Accrued interest payable					300,000				2,000,000				300,000	2,000,000
Conversion rate (per $1,000 principal amount of notes)	0.3215434
Conversion price (in dollars per share)	$ 3.11	$ 3.11
Notes balance				200,000,000	23,514,000	79,182,000	79,182,000	79,182,000	159,011,000	$ 159,011,000	$ 177,787,000	$ 200,000,000	23,514,000	159,011,000	$ 200,000,000	$ 200,000,000
Transactions costs																$ 12,700,000
Amortization of deferred debt costs	$ 3,600,000		2,000,000	$ 411,000	2,263,000	$ 252,000	$ 253,000	4,153,000	$ 506,000	1,544,000	1,899,000	$ 617,000	$ 6,900,000	$ 4,600,000
Debt conversion amount	$ 79,800,000		$ 55,700,000		$ 55,668,000			79,829,000		$ 18,776,000	$ 22,213,000
Percent of principal converted	50.00%		70.00%
Number of shares issued on conversion of debt (in shares)	35,300,000		20,500,000										56,600,000
Number of shares issued on conversion price excluding share issued for accrued interest (in shares)	25,600,000		17,900,000
Number of shares issued for accrued interest (in shares)	872,000
Five day average conversion price for accrued interest (in dollars per share)	$ 2.81
Common stock issued for interest on Notes	$ 2,400,000
Debt conversion expense (in shares)					2,600,000
Debt conversion expense					$ 14,500,000			$ 25,600,000