Balance Sheet Accounts (Schedule of Unrealized Losses and Fair Values by Investment Category and Time in Continuous Unrealized Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	$ 26,202
Less than 12 Months, Unrealized Losses	(75)
12 Months or More, Fair Value	0
12 Months or More, Unrealized Losses	0
Fair Value, Total	26,202
Unrealized Losses, Total	(75)
U.S. Corporate Debt Securities
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	26,202
Less than 12 Months, Unrealized Losses	(75)
12 Months or More, Fair Value	0
12 Months or More, Unrealized Losses	0
Fair Value, Total	26,202
Unrealized Losses, Total	$ (75)