Quarterly report pursuant to Section 13 or 15(d)

Leases - Additional Information (Detail)

v3.19.2
Leases - Additional Information (Detail)
$ in Thousands
1 Months Ended
Jan. 31, 2019
USD ($)
ft²
Jun. 30, 2019
USD ($)
Jan. 01, 2019
USD ($)
Dec. 31, 2018
USD ($)
Lessee Lease Description [Line Items]        
Lessee, operating leases remaining lease term.   7 years 2 months 12 days    
Lessee, finance leases remaining lease term.   1 year 2 months 12 days    
Area of land of additional facility lease agreement | ft² 57,000      
Lease expiration period 2028-08      
Operating lease right-of-use-asset $ 7,200 $ 10,796 $ 4,180 $ 0
Operating lease, lease liability 7,200 11,678    
Asset retirement obligation   $ 371,000    
Letter of Credit        
Lessee Lease Description [Line Items]        
Letter of credit $ 3,000      
Minimum        
Lessee Lease Description [Line Items]        
Lessee, operating leases remaining lease term.   1 year    
Lessee, finance leases remaining lease term.   1 year    
Lessee, operating leases renewal lease term   1 year    
Maximum        
Lessee Lease Description [Line Items]        
Lessee, operating leases remaining lease term.   10 years    
Lessee, finance leases remaining lease term.   2 years    
Lessee, operating leases renewal lease term   5 years