Marketable Securities (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2016 USD ($) Security	Dec. 31, 2015 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Number of securities below amortized cost basis	18
Number of securities	47
Proceeds from maturities of marketable securities | $	$ 32,155	$ 7,106
Current Assets
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, next twelve months, maximum year mature	1 year
Non-current Assets
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, year two through five, maximum year mature	2 years