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, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Dec. 31, 2010
6% Convertible Guaranteed Note [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 41,146,000		$ 41,146,000		$ 83,896,000	$ 115,000,000
Unamortized discount	(2,480,000)		(2,480,000)		(5,769,000)
Carrying amount of debt component	38,666,000		38,666,000		78,127,000
Carrying amount of equity component	(16,677,000)		(16,677,000)		3,654,000
Effective interest rate	8.10%		8.10%		8.10%
Aggregate if-converted value in excess of aggregate principal amount			29,135,000		42,579,000
Coupon interest	610,000	1,725,000	1,398,000	3,450,000
Discount amortization	175,000	484,000	398,000	969,000
Interest Expense	$ 785,000	$ 2,209,000	$ 1,796,000	$ 4,419,000