Annual report pursuant to Section 13 and 15(d)

Income Taxes - Additional Information (Detail)

v3.8.0.1
Income Taxes - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Jan. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Income Taxes [Line Items]        
U.S. federal statutory tax rate   34.00% 34.00% 34.00%
Percentage of TCJA limitations on net operating loss carryforwards to taxable income   80.00%    
Provision for income taxes related to alternative minimum tax     $ 0.1  
Federal        
Income Taxes [Line Items]        
Net operating loss carryforwards   $ 20.6    
Net operating loss carryforwards expiration period   Carried forward for 20 years and are expected to be available to fully offset taxable income earned in future tax years.    
Federal deferred tax provision   $ 8.8    
Federal deferred tax benefit   $ (9.2)    
Percentage of indefinite lived deferred tax liabilities recognized federal deferred tax benefit   80.00%    
Deferred tax benefit due to refundable AMT credits   $ 0.2    
Net operating loss carryforwards   $ 49.9 $ 21.0  
Net operating loss carryforwards expiration period   Expire between 2021 and 2037    
Federal | Indefinite Lived Deferred Income Tax Liabilities        
Income Taxes [Line Items]        
Federal deferred tax benefit   $ (0.7)    
State        
Income Taxes [Line Items]        
Net operating loss carryforwards   $ 36.3    
Net operating loss carryforwards expiration period   Expire between 2021 and 2037    
Scenario, forecast        
Income Taxes [Line Items]        
U.S. federal statutory tax rate 21.00%