Income Taxes - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Other deferred tax assets, net	$ 28,400,000	$ 23,100,000
Parent Company [Member]
Operating Loss Carryforwards [Line Items]
Valuation allowance related to the portion of operating loss carryforwards	$ 77,100,000
Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Tax years open for examination	2014
Latest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Tax years open for examination	2017
Le Mars [Member]
Operating Loss Carryforwards [Line Items]
Valuation allowance related to the portion of operating loss carryforwards	$ 264,467
Operating loss carryforwards	$ 1,600,000
Operating loss carryforwards expiration period	2020
Operating loss carryforwards annual limitations in amount on use	$ 376,000