Annual report pursuant to Section 13 and 15(d)

Intangible Assets - Additional Information (Detail)

v3.19.1
Intangible Assets - Additional Information (Detail) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Mar. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Mar. 31, 2019
Mar. 31, 2018
Mar. 31, 2017
Finite Lived Intangible Assets [Line Items]            
Intangible amortization expense       $ 237 $ 236 $ 234
Impairment losses, intangible assets       12,800 9,100  
Impairment losses, goodwill $ 1,222   $ 5,716      
Impairment of goodwill and intangible assets 6,449 $ 0 14,816 6,449 14,816  
Goodwill 0     0 1,222  
Permits [Member]            
Finite Lived Intangible Assets [Line Items]            
Impairment losses, intangible assets 1,700   8,600 10,300 8,600  
Tradename [Member]            
Finite Lived Intangible Assets [Line Items]            
Impairment losses, intangible assets 2,000   $ 500 2,500 500  
Customer Relationships [Member]            
Finite Lived Intangible Assets [Line Items]            
Intangible amortization expense       $ 180 $ 180 $ 180
Impairment losses, intangible assets 1,208          
Other Long-Lived Assets [Member]            
Finite Lived Intangible Assets [Line Items]            
Impairment losses, intangible assets $ 319