Marketable Securities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2013 Securities		Dec. 31, 2012	Sep. 30, 2013
Schedule of Available-for-sale Securities [Line Items]
Number of securities below amortized cost basis	68
Number of securities	77
Proceeds from maturities of marketable securities	$ 7,109		$ 17,473
Available-for-sale securities, amortized cost basis	57,361	[1]		64,471	[2]
Available-for-sale debt securities, unrealized gains	12			10
Available-for-sale debt securities, unrealized losses	(49)			(86)
Available-for-sale marketable securities	57,324	[1]		64,395	[2]
Purchased and accrued interest	446			629
Fair value of available-for-sale securities in continuous unrealized loss position for less than twelve months	44,863			48,544
Unrealized losses of available-for-sale securities in continuous unrealized loss position for less than twelve months	(48)			(85)
Fair value of available-for-sale securities in continuous unrealized loss position for twelve months or longer	1,815			2,001
Unrealized losses of available-for-sale securities in continuous unrealized loss position for twelve months or longer	(1)			(1)
Current Assets
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, next twelve months, maximum year mature	1 year
Available-for-sale securities, amortized cost basis	47,357	[1]		47,029	[2]
Available-for-sale debt securities, unrealized gains	12			10
Available-for-sale debt securities, unrealized losses	(28)			(33)
Available-for-sale marketable securities	47,341	[1]		47,006	[2]
Non-current Assets
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, year two through five, maximum year mature	3 years
Available-for-sale securities, amortized cost basis				17,442	[2]
Available-for-sale debt securities, unrealized gains				0
Available-for-sale debt securities, unrealized losses				(53)
Available-for-sale marketable securities				17,389	[2]
Corporate Bonds
Schedule of Available-for-sale Securities [Line Items]
Fair value of available-for-sale securities in continuous unrealized loss position for less than twelve months	27,230			29,911
Unrealized losses of available-for-sale securities in continuous unrealized loss position for less than twelve months	(23)			(35)
Fair value of available-for-sale securities in continuous unrealized loss position for twelve months or longer	1,815			2,001
Unrealized losses of available-for-sale securities in continuous unrealized loss position for twelve months or longer	(1)			(1)
Corporate Bonds | Current Assets
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis	37,060	[1]		35,161	[2]
Available-for-sale debt securities, unrealized gains	12			10
Available-for-sale debt securities, unrealized losses	(25)			(30)
Available-for-sale marketable securities	37,047	[1]		35,141	[2]
Corporate Bonds | Non-current Assets
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis				6,439	[2]
Available-for-sale debt securities, unrealized gains				0
Available-for-sale debt securities, unrealized losses				(6)
Available-for-sale marketable securities				6,433	[2]
Certificates of Deposit
Schedule of Available-for-sale Securities [Line Items]
Fair value of available-for-sale securities in continuous unrealized loss position for less than twelve months	12,226			12,451
Unrealized losses of available-for-sale securities in continuous unrealized loss position for less than twelve months	(24)			(49)
Fair value of available-for-sale securities in continuous unrealized loss position for twelve months or longer	0			0
Unrealized losses of available-for-sale securities in continuous unrealized loss position for twelve months or longer	0			0
Certificates of Deposit | Current Assets
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis	2,754	[1]		1,753	[2]
Available-for-sale debt securities, unrealized gains	0			0
Available-for-sale debt securities, unrealized losses	(2)			(2)
Available-for-sale marketable securities	2,752	[1]		1,751	[2]
Certificates of Deposit | Non-current Assets
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis	10,004	[1]		11,003	[2]
Available-for-sale debt securities, unrealized gains	0			0
Available-for-sale debt securities, unrealized losses	(21)			(47)
Available-for-sale marketable securities	9,983	[1]		10,956	[2]
Government Municipal Bonds
Schedule of Available-for-sale Securities [Line Items]
Fair value of available-for-sale securities in continuous unrealized loss position for less than twelve months	5,407			6,182
Unrealized losses of available-for-sale securities in continuous unrealized loss position for less than twelve months	(1)			(1)
Fair value of available-for-sale securities in continuous unrealized loss position for twelve months or longer	0			0
Unrealized losses of available-for-sale securities in continuous unrealized loss position for twelve months or longer	0			0
Government Municipal Bonds | Current Assets
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost basis	7,543	[1]		10,115	[2]
Available-for-sale debt securities, unrealized gains	0			0
Available-for-sale debt securities, unrealized losses	(1)			(1)
Available-for-sale marketable securities	$ 7,542	[1]		$ 10,114	[2]

[1] Included in amortized cost and fair value is purchased and accrued interest of $446

[2] Included in amortized cost and fair value is purchased and accrued interest of $629