Fair Value Measurements (Liabilitiles Measured on a Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011		Dec. 31, 2010
Liabilities measured at fair value on recurring basis, fair value hierarchy of valuation techniques
Common stock warrants, fair value	$ 0	$ 16,622	[1]
Level 1 [Member]
Liabilities measured at fair value on recurring basis, fair value hierarchy of valuation techniques
Common stock warrants, fair value	0	0	[1]
Level 2 [Member]
Liabilities measured at fair value on recurring basis, fair value hierarchy of valuation techniques
Common stock warrants, fair value	0	0	[1]
Level 3 [Member]
Liabilities measured at fair value on recurring basis, fair value hierarchy of valuation techniques
Common stock warrants, fair value	$ 0	$ 16,622	[1]	$ 26,193

[1] The fair value of the common stock warrants was estimated using a Black-Scholes option pricing model. See Note 13 for additional information regarding warrants.