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	Mar. 31, 2013
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	$ 32,942
12 Months or More, Fair Value	0
Fair Value, Total	32,942
Less than 12 Months, Unrealized Losses	(104)
12 Months or More, Unrealized Losses	0
Unrealized Losses, Total	(104)
U.S. Corporate Debt Securities
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	32,942
12 Months or More, Fair Value	0
Fair Value, Total	32,942
Less than 12 Months, Unrealized Losses	(104)
12 Months or More, Unrealized Losses	0
Unrealized Losses, Total	$ (104)