Fair Value Measurements (Details) - Fair value measurements on recurring basis - Total - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Assets:
Total fair value	$ 222,273	$ 224,094
Defined Benefit Pension Plans
Assets:
Total fair value	222,273	224,094
NAV
Assets:
Total fair value	222,273	224,094
NAV | Defined Benefit Pension Plans
Assets:
Total fair value	$ 222,273	$ 224,094