Debt - Additional disclosures related to the 6.00% Convertible Guaranteed Notes due 2030 (Details) - 6% Convertible Guaranteed Note [Member] - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2010
Debt Instrument [Line Items]
Principal amount of debt component	$ 12,400,000		$ 12,400,000	$ 115,000,000
Unamortized discount	(167,000)		(220,000)
Unamortized debt issuance costs	(41,000)		(54,000)
Carrying amount of debt component	12,192,000		12,126,000
Carrying amount of equity component	$ (34,784,000)		$ (34,784,000)
Effective interest rate	8.10%		7.80%
Aggregate if-converted value in excess of aggregate principal amount	$ 4,295,000		$ 2,863,000
Stated interest rate	6.00%		6.00%
Coupon interest	$ 186,000	$ 236,000
Discount amortization	53,000	67,000
Interest expense	$ 239,000	$ 303,000