Variable Interest Entities - Additional Information (Detail) In Millions, unless otherwise specified	12 Months Ended								12 Months Ended		1 Months Ended			1 Months Ended
	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2012 Limited Liability Company II [Member]	Dec. 31, 2012 Limited Liability Company [Member]	Dec. 31, 2012 Limited Liability Company [Member] Limited Liability Company II [Member] USD ($)	Dec. 31, 2011 Limited Liability Company [Member] Limited Liability Company II [Member] USD ($)	Dec. 31, 2000 Limited Liability Company [Member] Limited Liability Company II [Member] USD ($)	Dec. 31, 2012 Investment in Recycling and Waste to Energy USD ($)	Dec. 31, 2012 Investment in Recycling and Waste to Energy GBP (£)	Jan. 31, 2011 Investment in Refined Coal Facility [Member] USD ($)	Dec. 31, 2012 Investment in Refined Coal Facility [Member] USD ($)	Dec. 31, 2011 Investment in Refined Coal Facility [Member] USD ($)	Apr. 30, 2010 Low-Income Housing Properties [Member] USD ($)	Dec. 31, 2012 Low-Income Housing Properties [Member] USD ($)	Dec. 31, 2011 Low-Income Housing Properties [Member] USD ($)
Business Acquisition [Line Items]
Percentage of ownership in LLC's				0.25%	0.50%				50.00%	50.00%
Percentage of variable interest entities owned by other companies				99.75%	99.50%
Total initial investment by other companies								$ 167
Under the LLC agreements, the LLC shall be dissolved upon the occurrence of any of the following events	(i) a written decision of all members of the LLCs; (ii) December 31, 2063; (iii) a court's dissolution of the LLCs; or (iv) the LLCs ceasing to own any interest in the waste-to-energy facilities.
Reporting entity percentage of interest in earnings of variable interest entity after achieving targeted returns						80.00%
Other companies percentage of interest in earnings of variable interest entity after achieving targeted returns						20.00%
Net property and equipment						296	308
Noncontrolling Interest	321	320				245	246
Expense recognized for other companies' noncontrolling interests in LLCs' earnings	45	50	50
Expected cost to construct Waste-to-Energy LLC facility									325	200
Total commitment									93	57
Note receivables balance from the LLC									13	8
Investment balance	443	458								1		19	35		153	178
Cash payments to acquire equity method investment											48			6
Consideration for investment														221
Value of notes payable included in consideration for investment														215
Equity method investments debt balance															152	176
Variable interest entities primary beneficiary trust fair value assets	122	123
Carrying value of restricted trust funds and escrow accounts for which company is not the sole beneficiary specifically for future settlement of landfill and environmental remediation liabilities	$ 110	$ 107