Income Taxes - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2017 USD ($)
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ 76.3
Federal [Member]
Operating Loss Carryforwards [Line Items]
Federal income tax returns subject to examination description	Federal income tax returns of the Company are subject to IRS examination for the 2012 – 2016 tax years.
State [Member]
Operating Loss Carryforwards [Line Items]
Federal income tax returns subject to examination description	State income tax returns are subject to examination for a period of three to four years after filing.