Income Taxes - Additional information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Line Items]
Provision for income tax	$ 138
Net gain related to divestiture of Wheelabrator business	515
Equity in net losses of unconsolidated entities	(53)	(34)	(46)
Increase (decrease) deferred taxes and Accruals	24	4	7
Reduction in provision for income taxes due to tax audit settlements	12	11	10
Reduction in provision for income taxes due to state net operating loss and credit carry-forwards	16	16	5
Reduction in provision for income taxes due to Federal net operating loss carry-forwards			8
Increase (decrease) in provision for income taxes due to book impairments	8	235	7
Unremitted earnings in foreign subsidiaries	750
Increase in valuation allowance due to acquisition	151
Net unrecognized tax benefits that would impact effective tax rate in future period	28
Accrued interest	1	2	2
Accrued interest in balance sheet	3	7
Liabilities for unrecognized tax benefits including accrued interest that may be reversed within the next 12 months	12
Deferred tax assets related to unrecognized tax benefits that may be reversed within the next 12 months	3
Percentage of Bonus Depreciation allowance	50.00%
Federal [Member]
Income Taxes [Line Items]
Net operating loss carry-forwards	28
Operating loss carry-forwards, expiration date	Dec. 31, 2034
Capital loss carry-forward	519
Capital loss carry-forward, expiration date	Expire in 2019
State [Member]
Income Taxes [Line Items]
Net operating loss carry-forwards	1,600
Operating loss carry-forwards, expiration date	Dec. 31, 2034
State tax credit carry-forward	33
2013 Audit [Member]
Income Taxes [Line Items]
Expected time of completion of IRS audits	3 months
2014 Audit [Member]
Income Taxes [Line Items]
Expected time of completion of IRS audits	15 months
2015 Audit [Member]
Income Taxes [Line Items]
Expected time of completion of IRS audits	27 months
Investment in Refined Coal Facility [Member]
Income Taxes [Line Items]
Equity in net losses of unconsolidated entities	7	8	7
Income tax benefit, including tax credits, from equity method investment	21	20	21
Low-Income Housing Properties [Member]
Income Taxes [Line Items]
Equity in net losses of unconsolidated entities	25	25	24
Income tax benefit, including tax credits, from equity method investment	37	38	38
Interest expense	5	6	7
Tax credits from equity method investment	$ 25	$ 26	$ 26