Interest and Other Income - Other Income, Net (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Income Statement [Abstract]
Realized gain (loss) on sale of marketable securities, net	$ 2,076	$ (1,245)	$ 5,067	$ (29)
Realized loss on financial instrument obligation	(669)	0	(669)	0
Realized loss upon change to equity method at fair value	(568)	0	(568)	0
Other	(185)	(33)	(248)	(110)
Other income (expense), net	$ 654	$ (1,278)	$ 3,582	$ (139)