Cash, Cash Equivalents and Short-Term Investments (Details 1) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Maturities of short-term investments total, Amortized cost	$ 47,400	$ 51,710
Amortized Cost [Member]
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Securities amortized cost Due in one year or less	33,538	44,034
Amortized cost, Due after one year through two years	13,862	7,676
Maturities of short-term investments total, Amortized cost	47,400	51,710
Estimated Fair Value [Member]
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Securities fair value Due in one year or less	33,550	44,079
Estimated fair value, Due after one year through two years	13,879	7,661
Maturities of short-term investments total, Estimated fair value	$ 47,429	$ 51,740