Senior Convertible Notes - Narrative (Details) - USD ($)					1 Months Ended		3 Months Ended
	Mar. 01, 2017	Feb. 28, 2017	Mar. 18, 2016	Nov. 03, 2014	Mar. 31, 2017	Nov. 30, 2016	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Nov. 01, 2014
Debt Instrument [Line Items]
Debt conversion amount							$ 4,912,000		$ 82,274,000
Payment for indenture consent		$ 1,600,000
Debt conversion expense							$ 1,209,000		25,615,000
Common Shares
Debt Instrument [Line Items]
Debt conversion expense (in shares)							212,800
Convertible Senior Notes Due 2019
Debt Instrument [Line Items]
Aggregate principal amount	$ 18,600,000			$ 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
Conversion rate (per $1,000 principal amount of notes)			0.3215434
Conversion price (in dollars per share)			$ 3.11	$ 3.11
Transactions costs										$ 12,700,000
Debt conversion amount	$ 4,900,000		$ 79,800,000			$ 55,700,000	$ 4,911,000	$ 55,668,000	$ 79,829,000
Percent of principal converted			50.00%			70.00%
Number of shares issued on conversion of debt (in shares)	1,800,000		35,300,000			20,500,000
Number of shares issued on conversion price excluding share issued for accrued interest (in shares)			25,600,000			17,900,000
Debt conversion per original conversion price (in shares)					1,600,000			2,600,000	9,600,000
Debt conversion expense								$ 14,500,000	$ 25,600,000