Debt - Additional disclosures related to the 6.00% Convertible Guaranteed Notes due 2030 (Details) - 6% Convertible Guaranteed Note [Member] - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	Dec. 31, 2010
Debt Instrument [Line Items]
Stated interest rate	6.00%		6.00%		6.00%
Principal amount of debt component	$ 12,800,000		$ 12,800,000		$ 16,228,000	$ 115,000,000
Unamortized discount	(336,000)		(336,000)		(564,000)
Carrying amount of debt component	12,464,000		12,464,000		15,664,000
Carrying amount of equity component	$ (34,681,000)		$ (34,681,000)		$ (33,160,000)
Effective interest rate	7.60%		7.60%		8.10%
Aggregate if-converted value in excess of aggregate principal amount			$ 3,655,000		$ 10,432,000
Coupon interest	$ 156,000	$ 393,000	392,000	$ 821,000
Discount amortization	55,000	112,000	122,000	233,000
Interest expense	$ 211,000	$ 505,000	$ 514,000	$ 1,054,000