Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Valuation allowance against deferred tax assets		100.00%
Gross federal net operating loss carry forwards			$ 284.8
Gross federal estimated net operating loss carry forwards		$ 62.8
Gross state net operating loss carry forwards			$ 196.6
Gross state estimated net operating loss carry forwards		$ 62.8
U.S. federal statutory rate	35.00%	21.00%	34.00%
Revaluation provision to income tax expense		$ 37.0