Subsequent Events (Details) - USD ($)					1 Months Ended	3 Months Ended				12 Months Ended
	Mar. 01, 2017	Feb. 28, 2017	Jan. 31, 2017	Mar. 18, 2016	Nov. 30, 2016	Dec. 31, 2016	Mar. 31, 2016	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Nov. 03, 2014
Subsequent Event [Line Items]
Debt conversion amount										$ 137,941,000	$ 40,989,000	$ 0
Convertible Senior Notes Due 2019
Subsequent Event [Line Items]
Debt conversion amount				$ 79,800,000	$ 55,700,000	$ 55,668,000	$ 79,829,000	$ 18,776,000	$ 22,213,000
Number of shares issued on conversion of debt (in shares)				35,300,000	20,500,000					56,600,000
Debt conversion expense (in shares)						2,600,000
Conversion price (in dollars per share)				$ 3.11									$ 3.11
Aggregate principal amount						$ 23,500,000				$ 23,500,000	$ 159,000,000	$ 200,000,000	$ 200,000,000
Subsequent Event
Subsequent Event [Line Items]
Payment for indenture consent		$ 1,600,000
Subsequent Event | Convertible Senior Notes Due 2019
Subsequent Event [Line Items]
Debt conversion amount	$ 4,000,000
Number of shares issued on conversion of debt (in shares)	1,500,000
Debt conversion expense (in shares)	1,300,000
Aggregate principal amount	$ 19,500,000
Subsequent Event | Public stock offering
Subsequent Event [Line Items]
Number of shares issued/sold in transaction			20,325,204
Public offering price (in dollars per share)			$ 6.15
Proceeds yielded from offering			$ 121,600,000