Convertible Senior Notes (Details) (USD $)	3 Months Ended	0 Months Ended	2 Months Ended	3 Months Ended	0 Months Ended
	Mar. 31, 2015	Nov. 03, 2014	Dec. 31, 2014	Mar. 31, 2014	Nov. 01, 2015	May 01, 2015	Nov. 01, 2014
Convertible Senior Notes
Interest payable on Senior Convertible Debentures	$ 6,250,000		$ 2,500,000
Amortization schedule
Less: amortization	(617,000)
Deferred financing costs, Balance at the end of the period	11,719,000		12,336,000
Convertible Senior Notes Due 2019
Convertible Senior Notes
Aggregate principal amount (in dollars)		200,000,000
Interest rate (as a percent)		7.50%
Additional aggregate principal amount pertaining to the over-allotment option granted (in dollars)		25,000,000
Net proceeds from offering (in dollars)		187,300,000
Interest payable on Senior Convertible Debentures	6,300,000		2,500,000
Conversion rate (as a percent)		0.3215434
Conversion price (in dollars per share)		$ 3.11
Amortization schedule
Deferred financing costs at issuance							12,747,000
Less: amortization	(617,000)		(411,000)	0
Deferred financing costs, Balance at the end of the period	11,719,000		12,336,000
Convertible Senior Notes Due 2019 | Forecast
Convertible Senior Notes
Semiannual interest payment					7,500,000
Convertible Senior Notes Due 2019 | Subsequent Event
Convertible Senior Notes
Semiannual interest payment						$ 7,400,000
Period from note issuance date to the date of first semiannual interest payment						178 days