Annual report pursuant to Section 13 and 15(d)

Intangible Assets - Summary of Intangible Assets (Detail)

v3.19.1
Intangible Assets - Summary of Intangible Assets (Detail) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2019
Dec. 31, 2017
Mar. 31, 2019
Mar. 31, 2018
Schedule Of Intangible Assets [Line Items]        
Intangibles not subject to amortization, Gross Carrying Amount $ 12,800   $ 12,800 $ 12,800
Intangibles not subject to amortization, Impairment Loss     12,800 9,100
Intangibles not subject to amortization, Net Carrying Amount 0   0 3,700
Permits [Member]        
Schedule Of Intangible Assets [Line Items]        
Intangibles not subject to amortization, Gross Carrying Amount 10,300   10,300 10,300
Intangibles not subject to amortization, Impairment Loss 1,700 $ 8,600 10,300 8,600
Intangibles not subject to amortization, Net Carrying Amount       1,700
Tradename [Member]        
Schedule Of Intangible Assets [Line Items]        
Intangibles not subject to amortization, Gross Carrying Amount 2,500   2,500 2,500
Intangibles not subject to amortization, Impairment Loss 2,000 $ 500 2,500 500
Intangibles not subject to amortization, Net Carrying Amount       2,000
Customer Relationships [Member]        
Schedule Of Intangible Assets [Line Items]        
Intangibles subject to amortization, Gross Carrying Amount 2,700   2,700 2,700
Intangibles subject to amortization, Accumulated Amortization 1,492   1,492 1,312
Intangibles subject to amortization, Impairment Loss     $ 1,208  
Intangibles subject to amortization, Net Carrying Amount       $ 1,388
Intangibles not subject to amortization, Impairment Loss $ 1,208