Senior Convertible Notes - Narrative (Details) - USD ($)			2 Months Ended	3 Months Ended							9 Months Ended
	Mar. 18, 2016	Nov. 03, 2014	Dec. 31, 2014	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2016	Sep. 30, 2015	Nov. 01, 2014
Debt Instrument [Line Items]
Accrued interest payable				$ 2,474,000			$ 1,988,000				$ 2,474,000
Amortization of deferred debt costs											4,658,000	$ 4,060,000
Debt conversion amount											82,274,000	40,989,000
Common stock issued for interest on Notes											2,445,000	0
Debt conversion expense				0				$ 0			25,615,000	0
Common Shares
Debt Instrument [Line Items]
Debt conversion expense (in shares)	9,593,751
Convertible Senior Notes Due 2019
Debt Instrument [Line Items]
Aggregate principal amount		$ 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				1,500,000				2,700,000			5,900,000	9,900,000
Accrued interest payable				2,500,000			2,000,000				2,500,000
Conversion rate (per $1,000 principal amount of notes)	0.3215434
Conversion price (in dollars per share)	$ 3.11
Notes balance			$ 200,000,000	79,182,000	$ 79,182,000	$ 79,182,000	159,011,000	159,011,000	$ 177,787,000	$ 200,000,000	79,182,000	159,011,000	$ 200,000,000
Transactions costs													$ 12,700,000
Amortization of deferred debt costs	$ 3,600,000		$ 411,000	$ 252,000	$ 253,000	4,153,000	$ 506,000	1,544,000	1,899,000	$ 617,000	$ 4,700,000	$ 4,100,000
Debt conversion amount	$ 79,800,000					$ 79,829,000		$ 18,776,000	$ 22,213,000
Percent of principal converted	50.00%
Number of shares issued on conversion of debt (in shares)	35,300,000
Number of shares issued on conversion price excluding share issued for accrued interest (in shares)	25,600,000
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