Fair Value Measurements (Fair Value of Assets and Liabilities Measured on Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Sep. 30, 2016
Assets:
Cash equivalents	$ 23,110	$ 435
Short-term investments	14,874,000
Deferred compensation	5,703	5,773
Liabilities:
Deferred compensation	4,441	4,449
Fair Value, Inputs, Level 1
Assets:
Cash equivalents	23,110	435
Short-term investments	14,874,000
Deferred compensation	0	1,643
Fair Value, Inputs, Level 2
Assets:
Deferred compensation	5,703	4,130
Liabilities:
Deferred compensation	$ 4,441	$ 4,449