Summary of Significant Accounting Policies (Details 5) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Summary of Significant Accounting Policies
Net loss	$ (3,654)	$ (145)	$ (1,908)	$ (3,895)	$ (3,686)	$ (3,967)	$ 3,319	$ (12,416)	$ (9,602)	$ (16,750)	$ (77,069)
Weighted average common shares outstanding									21,703	21,392	21,189
Net loss per share:
Basic and diluted (in dollars per share)	$ (0.17)	$ (0.01)	$ (0.09)	$ (0.18)					$ (0.44)	$ (0.78)	$ (3.64)
Anti-dilutive securities excluded from the computation of diluted net loss per share
Anti-dilutive securities (in shares)									3,285	2,564	2,486
Options to purchase shares of common stock
Anti-dilutive securities excluded from the computation of diluted net loss per share
Anti-dilutive securities (in shares)									2,820	2,190	1,817
Shares of common stock issuable upon the vesting of restricted stock units
Anti-dilutive securities excluded from the computation of diluted net loss per share
Anti-dilutive securities (in shares)									465	374	669