Commitments and Contingencies (Narrative) (Detail) $ / d in Thousands, T in Millions	3 Months Ended	6 Months Ended	7 Months Ended	12 Months Ended	36 Months Ended
	Mar. 31, 2018 USD ($)	Jun. 30, 2018 USD ($) $ / d	Jul. 25, 2017 USD ($)	Dec. 31, 2016 T	Sep. 30, 2014 USD ($)	Jan. 05, 2017 USD ($)	Dec. 31, 2014 USD ($)
Contingencies And Commitments [Line Items]
Estimated clean up costs							$ 342,000,000
Solid Waste Management Fee Enforcement Order [Member]
Contingencies And Commitments [Line Items]
Loss contingency amount sought					$ 5,100,000
Bridge and Thoroughfare Fee [Member]
Contingencies And Commitments [Line Items]
Loss contingency amount sought	$ 83,000		$ 11,600,000
Noncompliance fee	$ 750
Penalties accrued per day | $ / d		1
Chiquita Canyon, LLC [Member]
Contingencies And Commitments [Line Items]
Annual tons of waste accepted at landfill | T				3
Estimate of total new fees and other new taxes over the life of the conditional use permit		$ 300,000,000
Environmental Remediation Expense [Member]
Contingencies And Commitments [Line Items]
Estimated period to implement clean-up		seven years
Required period of monitoring following the clean-up		10 years
Progressive Waste Solutions Ltd. [Member] | Florida Default Judgment [Member]
Contingencies And Commitments [Line Items]
Estimated loss from final judgment						$ 10,000,000