Income Taxes (Components of Deferred Tax Assets and Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Deferred tax assets:
Net operating losses	$ 67,507	$ 54,923
Credits	4,194	3,329
Deferred revenues	1,198	1,297
Stock-based compensation	3,043	4,464
Reserves and accruals	3,626	2,090
Depreciation	2,247	1,746
Intangible assets	4,208	3,556
Unrealized gain/loss	112	166
Other assets	159	141
Total deferred tax assets:	86,294	71,712
Deferred tax liabilities:
Other	0	0
Total deferred tax liabilities:	0	0
Valuation allowance	(86,294)	(71,692)
Net deferred tax assets	$ 0	$ 20