Marketable Securities (Fair Value to Amortized Cost) (Details) - USD ($) $ in Thousands		Jun. 30, 2015		Sep. 30, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis		$ 47,031	[1]	$ 44,471	[2]
Available-for-sale securities, unrealized gains		17		17
Available-for-sale securities, unrealized losses		(50)		(49)
Available-for-sale marketable securities, fair value		46,998	[1]	44,439	[2]
Purchased and accrued interest		262		213
Current Assets
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis		37,558	[1]	32,918	[2]
Available-for-sale securities, unrealized gains		4		3
Available-for-sale securities, unrealized losses		(35)		(23)
Available-for-sale marketable securities, fair value		37,527	[1]	32,898	[2]
Current Assets | Corporate Bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis		28,065	[1]	24,668	[2]
Available-for-sale securities, unrealized gains		0		1
Available-for-sale securities, unrealized losses		(31)		(22)
Available-for-sale marketable securities, fair value		28,034	[1]	24,647	[2]
Current Assets | Commercial Paper
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis		3,991	[1]	3,998	[2]
Available-for-sale securities, unrealized gains		0		0
Available-for-sale securities, unrealized losses		(4)		(1)
Available-for-sale marketable securities, fair value		3,987	[1]	3,997	[2]
Current Assets | Certificates of Deposit
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis		5,502	[1]	4,252	[2]
Available-for-sale securities, unrealized gains		4		2
Available-for-sale securities, unrealized losses		0		0
Available-for-sale marketable securities, fair value		5,506	[1]	4,254	[2]
Non-current Assets
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis		9,473	[1]	11,553	[2]
Available-for-sale securities, unrealized gains		13		14
Available-for-sale securities, unrealized losses		(15)		(26)
Available-for-sale marketable securities, fair value		9,471	[1]	11,541	[2]
Non-current Assets | Corporate Bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis		3,723	[1]	2,051	[2]
Available-for-sale securities, unrealized gains		0		0
Available-for-sale securities, unrealized losses		(14)		(4)
Available-for-sale marketable securities, fair value		3,709	[1]	2,047	[2]
Non-current Assets | Certificates of Deposit
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis		4,504	[1]	9,502	[2]
Available-for-sale securities, unrealized gains		13		14
Available-for-sale securities, unrealized losses		0		(22)
Available-for-sale marketable securities, fair value		4,517	[1]	$ 9,494	[2]
Non-current Assets | Government municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis	[1]	1,246
Available-for-sale securities, unrealized gains		0
Available-for-sale securities, unrealized losses		(1)
Available-for-sale marketable securities, fair value	[1]	$ 1,245

[1] Included in amortized cost and fair value is purchased and accrued interest of $262

[2] Included in amortized cost and fair value is purchased and accrued interest of $213.