Basis of Presentation - Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Balance as of December 31, 2013			$ 8,820
Foreign currency translation adjustments during period	(652)	963	(137)	(331)
Unrealized gain (loss) on investments during period	(7,089)	4,903	(10,146)	(3,501)
Current period other comprehensive income (loss)	(7,741)	5,866	(10,283)	(3,832)
Balance as of September 30, 2014	(1,463)		(1,463)
Foreign Currency Translation Adjustments
Balance as of December 31, 2013			1,215
Foreign currency translation adjustments during period			(137)
Balance as of September 30, 2014	1,078		1,078
Unrealized Gain (Loss) on Investments
Balance as of December 31, 2013			7,605
Unrealized gain (loss) on investments during period			(10,146)
Balance as of September 30, 2014	(2,541)		(2,541)
Accumulated Other Comprehensive Income (Loss)
Balance as of December 31, 2013			8,820
Current period other comprehensive income (loss)			(10,283)
Balance as of September 30, 2014	$ (1,463)		$ (1,463)