Landfill and Environmental Remediation Liabilities - Changes to Landfill and Environmental Remediation Liabilities (Parenthetical) (Detail) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2016	Dec. 31, 2015
Environmental Remediation Obligations [Abstract]
Risk-free discount rate of the obligations	1.50%	2.25%
Increase (Decrease) to operating expenses due to change in discount rate used to estimate the present value of environmental remediation obligations	$ 9

Rate applied to the undiscounted amount of environmental loss contingencies to arrive at the present value recorded as of the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 5.Y.Q1)
-URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 5
-Section Y
-Paragraph Question 1

Name:	us-gaap_AccrualForEnvironmentalLossContingenciesDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant