Marketable Securities (Details) (U.S. corporate bonds, USD $) In Thousands, unless otherwise specified	Sep. 30, 2013
Short-term Marketable Securities
Marketable Securities
Fair Value	$ 69,792
Cost	69,772
Unrealized Gain	34
Unrealized Loss	(14)
Long-term Marketable Securities
Marketable Securities
Fair Value	26,068
Cost	26,050
Unrealized Gain	18
Unrealized Loss	$ 0