Marketable Securities (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 10,912		$ 11,198
Level 1 Fair Value [Member]
Schedule of Held-to-maturity Securities [Line Items]
Level 1 Fair Value	10,910	[1]	11,191	[1]
Agency bonds [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1,001		2,605
Agency bonds [Member] | Level 1 Fair Value [Member]
Schedule of Held-to-maturity Securities [Line Items]
Level 1 Fair Value	1,001	[1]	2,605	[1]
Certificates of deposit [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	900		900
Certificates of deposit [Member] | Level 1 Fair Value [Member]
Schedule of Held-to-maturity Securities [Line Items]
Level 1 Fair Value	900	[1]	899	[1]
Commercial paper [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	3,594		3,097
Commercial paper [Member] | Level 1 Fair Value [Member]
Schedule of Held-to-maturity Securities [Line Items]
Level 1 Fair Value	3,595	[1]	3,096	[1]
Corporate Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	5,417		4,596
Corporate Debt Securities [Member] | Level 1 Fair Value [Member]
Schedule of Held-to-maturity Securities [Line Items]
Level 1 Fair Value	$ 5,414	[1]	$ 4,591	[1]

[1] Level 1 fair values are defined as observable inputs such as quoted prices in active markets.