Goodwill and Other Intangibles - Intangible Assets Subject to Amortization (Detail) $ in Thousands	Sep. 30, 2018 USD ($)
Finite Lived Intangible Assets [Line Items]
Gross Amount	$ 559,870
Accumulated Amortization	(80,981)
Net Balance	478,889
Noncompetition agreements
Finite Lived Intangible Assets [Line Items]
Gross Amount	12,024
Accumulated Amortization	(11,105)
Net Balance	919
Customer Relationships
Finite Lived Intangible Assets [Line Items]
Gross Amount	56,530
Accumulated Amortization	(18,325)
Net Balance	38,205
Operating Permits
Finite Lived Intangible Assets [Line Items]
Gross Amount	458,952
Accumulated Amortization	(31,375)
Net Balance	427,577
Use Rights And Other
Finite Lived Intangible Assets [Line Items]
Gross Amount	19,564
Accumulated Amortization	(10,789)
Net Balance	8,775
Trade names
Finite Lived Intangible Assets [Line Items]
Gross Amount	12,800
Accumulated Amortization	(9,387)
Net Balance	$ 3,413