Basis of Presentation - Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Balance as of December 31, 2013	$ 8,820
Foreign currency translation adjustments during period	93	(1,381)
Unrealized loss on investments during period	(4,552)	(4,858)
Current period other comprehensive loss	(4,459)	(6,239)
Balance as of March 31, 2014	4,361
Foreign Currency Translation Adjustments
Balance as of December 31, 2013	1,215
Foreign currency translation adjustments during period	93
Balance as of March 31, 2014	1,308
Unrealized Gain (Loss) on Investments
Balance as of December 31, 2013	7,605
Unrealized loss on investments during period	(4,552)
Balance as of March 31, 2014	3,053
Accumulated Other Comprehensive Income
Balance as of December 31, 2013	8,820
Current period other comprehensive loss	(4,459)
Balance as of March 31, 2014	$ 4,361