Description of Business and Summary of Significant Accounting Policies (Computation of basic and diluted net income (loss) per share) (Details) (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
Schedule of computation of basic and diluted net income (loss) per share
Net income (loss)	$ (2,814)	[1]	$ 6,027	[2]	$ 3,405	[3]	$ (278)	[4]	$ 2,867	[5]	$ 5,228	[6]	$ 31	[7]	$ (952)	[8]	$ 6,340	$ 7,174	$ (1,438)
Effect of assumed conversion of convertible debentures
Weighted average common shares outstanding																	28,869	28,568	27,637
Weighted average common shares outstanding, assuming dilution																	28,903	28,709	27,637
Net income (loss) per share:
Basic (in dollars per share)																	$ 0.22	$ 0.25	$ (0.05)
Diluted (in dollars per share)																	$ 0.22	$ 0.25	$ (0.05)
Options to purchase common stock [Member]
Effect of assumed conversion of convertible debentures
Effect of potentially dilutive securities																	16	115	0
Restricted Stock Awards [Member]
Effect of assumed conversion of convertible debentures
Effect of potentially dilutive securities																	3	10	0
Restricted stock unit awards [Member]
Effect of assumed conversion of convertible debentures
Effect of potentially dilutive securities																	14	2	0
Employee Stock Purchase Plan [Member]
Effect of assumed conversion of convertible debentures
Effect of potentially dilutive securities																	1	14	0

[1] Includes a non-cash expense for stock-based compensation of $1.4 million.

[2] Includes a non-cash expense for stock-based compensation of $719,000.

[3] Includes a non-cash expense for stock-based compensation of $946,000.

[4] Includes a non-cash expense for stock-based compensation of $1.0 million.

[5] Includes a non-cash expense for stock-based compensation of $527,000.

[6] Includes a non-cash expense for stock-based compensation of $505,000.

[7] Includes a non-cash expense for stock-based compensation of $770,000

[8] Includes a non-cash expense for stock-based compensation of $1.3 million.