Cash and Cash Equivalents and Short-term Investments (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Gross unrealized losses of cash and cash equivalents and short-term investments
Available-for-sale securities, less than 12 months	$ 19,917
Available-for-sale securities, gross unrealized loss, less than 12 months	2,102
Available-for-sale securities, more than 12 months	2,577
Available-for-sale securities, gross unrealized loss, more than 12 months	246
Debt Securities [Member]
Gross unrealized losses of cash and cash equivalents and short-term investments
Available-for-sale securities, less than 12 months	19,917
Available-for-sale securities, gross unrealized loss, less than 12 months	2,102
Available-for-sale securities, more than 12 months	2,577
Available-for-sale securities, gross unrealized loss, more than 12 months	246
Equity Securities [Member]
Gross unrealized losses of cash and cash equivalents and short-term investments
Available-for-sale securities, less than 12 months	0
Available-for-sale securities, gross unrealized loss, less than 12 months	0
Available-for-sale securities, more than 12 months	0
Available-for-sale securities, gross unrealized loss, more than 12 months	0
Corporate debt securities [Member]
Gross unrealized losses of cash and cash equivalents and short-term investments
Available-for-sale securities, less than 12 months	17,700
Available-for-sale securities, gross unrealized loss, less than 12 months	2,095
Available-for-sale securities, more than 12 months	0
Available-for-sale securities, gross unrealized loss, more than 12 months	0
Mortgage-CMO debt securities [Member]
Gross unrealized losses of cash and cash equivalents and short-term investments
Available-for-sale securities, less than 12 months	2,217
Available-for-sale securities, gross unrealized loss, less than 12 months	7
Available-for-sale securities, more than 12 months	83
Available-for-sale securities, gross unrealized loss, more than 12 months	8
Asset-backed debt securities [Member]
Gross unrealized losses of cash and cash equivalents and short-term investments
Available-for-sale securities, less than 12 months	0
Available-for-sale securities, gross unrealized loss, less than 12 months	0
Available-for-sale securities, more than 12 months	2,494
Available-for-sale securities, gross unrealized loss, more than 12 months	$ 238