Marketable Securities (Fair Value to Amortized Cost) (Details) - USD ($) $ in Thousands		Dec. 31, 2015		Sep. 30, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis		$ 61,848	[1]	$ 60,869	[2]
Available-for-sale securities, unrealized gains		2		10
Available-for-sale securities, unrealized losses		(124)		(62)
Available-for-sale marketable securities, fair value		61,726	[1]	60,817	[2]
Purchased and accrued interest		374		252
Current Assets
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis		50,271	[1]	47,224	[2]
Available-for-sale securities, unrealized gains		2		8
Available-for-sale securities, unrealized losses		(71)		(41)
Available-for-sale marketable securities, fair value		50,202	[1]	47,191	[2]
Current Assets | Corporate Bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis		32,844	[1]	31,753	[2]
Available-for-sale securities, unrealized gains		1		0
Available-for-sale securities, unrealized losses		(60)		(39)
Available-for-sale marketable securities, fair value		32,785	[1]	31,714	[2]
Current Assets | Commercial Paper
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis		7,990	[1]	7,986	[2]
Available-for-sale securities, unrealized gains		0		0
Available-for-sale securities, unrealized losses		(6)		(1)
Available-for-sale marketable securities, fair value		7,984	[1]	7,985	[2]
Current Assets | Certificates of Deposit
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis		6,257	[1]	6,253	[2]
Available-for-sale securities, unrealized gains		1		8
Available-for-sale securities, unrealized losses		0		0
Available-for-sale marketable securities, fair value		6,258	[1]	6,261	[2]
Current Assets | Government municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis		3,180	[1]	1,232	[2]
Available-for-sale securities, unrealized gains		0		0
Available-for-sale securities, unrealized losses		(5)		(1)
Available-for-sale marketable securities, fair value		3,175		1,231
Non-current Assets
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis		11,577	[1]	13,645	[2]
Available-for-sale securities, unrealized gains		0		2
Available-for-sale securities, unrealized losses		(53)		(21)
Available-for-sale marketable securities, fair value		11,524	[1]	13,626	[2]
Non-current Assets | Corporate Bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis		4,051	[1]	4,138	[2]
Available-for-sale securities, unrealized gains		0		0
Available-for-sale securities, unrealized losses		(29)		(12)
Available-for-sale marketable securities, fair value		4,022	[1]	4,126	[2]
Non-current Assets | Certificates of Deposit
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis		7,526	[1]	7,511	[2]
Available-for-sale securities, unrealized gains		0		2
Available-for-sale securities, unrealized losses		(24)		(6)
Available-for-sale marketable securities, fair value		$ 7,502	[1]	7,507	[2]
Non-current Assets | Government municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis	[2]			1,996
Available-for-sale securities, unrealized gains				0
Available-for-sale securities, unrealized losses				(3)
Available-for-sale marketable securities, fair value	[2]			$ 1,993

[1] Included in amortized cost and fair value is purchased and accrued interest of $374

[2] Included in amortized cost and fair value is purchased and accrued interest of $252.