Debt - Additional disclosures related to the 6.00% Convertible Guaranteed Notes due 2030 (Details) - 6% Convertible Guaranteed Note [Member] - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2010
Debt Instrument [Line Items]
Principal amount of debt component	$ 12,400,000		$ 12,400,000		$ 16,228,000	$ 115,000,000
Unamortized discount	(272,000)		(272,000)		(564,000)
Carrying amount of debt component	12,128,000		12,128,000		15,664,000
Carrying amount of equity component	$ (34,784,000)		$ (34,784,000)		$ (33,160,000)
Effective interest rate	7.70%		7.70%		8.10%
Aggregate if-converted value in excess of aggregate principal amount			$ 3,054,000		$ 10,432,000
Stated interest rate	6.00%		6.00%		6.00%
Coupon interest	$ 185,000	$ 375,000	$ 577,000	$ 1,196,000
Discount amortization	53,000	107,000	175,000	340,000
Interest expense	$ 238,000	$ 482,000	$ 752,000	$ 1,536,000