Marketable Securities (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended		12 Months Ended
	Jun. 30, 2013 Securities		Sep. 30, 2012
Schedule of Available-for-sale Securities [Line Items]
Number of securities below amortized cost basis	62
Number of securities	71
Amortized cost	$ 57,998	[1]	$ 60,401	[2]
Unrealized gains	8		15
Unrealized losses	(92)	[3]	(28)	[4]
Available-for-sale marketable securities	57,914	[1]	60,388	[2]
Purchased and accrued interest	388		485
Aggregate related fair value of securities with unrealized losses	47,140		34,503
Current Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Maturity period, next twelve months	1 year
Amortized cost	44,849	[1]	58,382	[2]
Unrealized gains	8		15
Unrealized losses	(51)	[3]	(25)	[4]
Available-for-sale marketable securities	44,806	[1]	58,372	[2]
Non-current Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Maturity period, year two through five	3 years
Amortized cost	13,149	[1]
Unrealized gains	0
Unrealized losses	(41)	[3]
Available-for-sale marketable securities	13,108	[1]
Corporate Bonds [Member] | Current Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	34,163		39,306
Unrealized gains	6		14
Unrealized losses	(47)		(19)
Available-for-sale marketable securities	34,122	[1]	39,301	[2]
Corporate Bonds [Member] | Non-current Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	2,030		2,019
Unrealized gains	0		0
Unrealized losses	(5)		(3)
Available-for-sale marketable securities	2,025	[1]	2,016	[2]
Commercial Paper [Member] | Current Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost			2,000
Unrealized gains			0
Unrealized losses			0
Available-for-sale marketable securities			2,000	[2]
Certificates of Deposit [Member] | Current Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	3,004		7,262
Unrealized gains	0		0
Unrealized losses	(3)		(4)
Available-for-sale marketable securities	3,001	[1]	7,258	[2]
Certificates of Deposit [Member] | Non-current Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	8,002
Unrealized gains	0
Unrealized losses	(34)
Available-for-sale marketable securities	7,968	[1]
Government Municipal Bonds [Member] | Current Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	7,682		9,814
Unrealized gains	2		1
Unrealized losses	(1)		(2)
Available-for-sale marketable securities	7,683	[1]	9,813	[2]
Government Municipal Bonds [Member] | Non-current Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	3,117
Unrealized gains	0
Unrealized losses	(2)
Available-for-sale marketable securities	$ 3,115	[1]

[1] Included in amortized cost and fair value is purchased and accrued interest of $388

[2] Included in amortized cost and fair value is purchased and accrued interest of $485

[3] The aggregate related fair value of securities with unrealized losses as of June 30, 2013 was $47,140. These investments have been in an unrealized loss position for less than twelve months.

[4] The aggregate related fair value of securities with unrealized losses as of September 30, 2012 was $34,503. These investments have been in an unrealized loss position for less than twelve months.