Leases, User Charges and Commitments - Schedule of Future Minimum Lease Payments Under Operating and Finance Leases (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Leases [Abstract]
Operating Leases Liability, Less Than 1 year	$ 9,868
Operating Leases Liability, 1 - 3 years	16,205
Operating Leases Liability, 3 - 5 years	9,194
Operating Leases Liability, Over 5 years	7,933
Operating Leases Liability, Minimum lease payments	43,200
Operating Leases Liability, Imputed interest	4,091
Operating Leases Liability, Present value of minimum lease payments	39,109
Less: Operating Leases Liability, Current lease liabilities	8,665
Operating Leases Liability, Long-term lease liabilities	30,444
Finance Lease Liability, Less Than 1 Year	3,186
Finance Lease Liability, 1 - 3 Years	2,645
Finance Lease Liability, 3 - 5 years	2
Finance Leases Liability, Minimum lease payments	5,833
Finance Leases Liability, Imputed interest	212
Finance Leases Liability, Present value of minimum lease payments	5,621
Less: Finance Leases Liability, current lease liabilities	3,021	$ 2,845
Finance Leases Liability, Long-term lease liabilities	$ 2,600	$ 4,739