Organization and Basis of Presentation (Details) T in Millions, MW in Millions, $ in Millions		3 Months Ended
	Jan. 01, 2018 USD ($)	Mar. 31, 2018 USD ($) MW T Segment Facility	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Organization And Summary Of Significant Accounting Policies [Line Items]
Solid waste processed (in tons) | T		20
Number Of Energy From Waste Facilities | Facility		42
Annual Output | MW		10
Number Of Reportable Business Segments | Segment		1
Revenues		$ 458	$ 404
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents		51	444	$ 46
Restricted funds included in held for sale				77
Restricted funds held in trust- short term		42	52	43
Restricted funds held in trust- long term		23	52	28
Beginning of period balance presented in the statement of cash flows		116	548	194	$ 194
Statement of Cash Flows [Abstract]
Cash provided by operating activities		3	9
Cash used in investing activities		26	(77)
Cash provided by financing activities		(110)	421
Accounting Standards Update 2014-09 [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Net decrease to beginning accumulated deficit	$ 1
Revenues		$ 1
Scenario, Previously Reported [Member] | Accounting Standards Update 2016-18 [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents				46
Restricted funds included in held for sale				0
Restricted funds held in trust- short term				0
Restricted funds held in trust- long term				0
Beginning of period balance presented in the statement of cash flows				$ 46
Statement of Cash Flows [Abstract]
Cash provided by operating activities			10
Cash used in investing activities			(77)
Cash provided by financing activities			$ 426