Basis of Presentation - Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Balance as of December 31, 2012			$ 13,286
Foreign currency translation adjustments during period	963	503	(331)	664
Unrealized gain (loss) on investments during period	4,903	(1,940)	(3,501)	(6,352)
Current period other comprehensive loss	5,866	(1,437)	(3,832)	(5,688)
Balance as of September 30, 2013	9,454		9,454
Foreign Currency Translation Adjustments
Balance as of December 31, 2012			1,055
Foreign currency translation adjustments during period			(331)
Balance as of September 30, 2013	724		724
Unrealized Gain (Loss) on Investments
Balance as of December 31, 2012			12,231
Unrealized gain (loss) on investments during period			(3,501)
Balance as of September 30, 2013	8,730		8,730
Accumulated Other Comprehensive Income
Balance as of December 31, 2012			13,286
Current period other comprehensive loss			(3,832)
Balance as of September 30, 2013	$ 9,454		$ 9,454