Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

No definition available.

Name:	us-gaap_NumberOfOperatingSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Business Segments (Narrative) (Details) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
Business Segments (Narrative) (Details) $ in Millions	Sep. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) segment	Sep. 30, 2017 USD ($)
Segment Reporting [Abstract]
Number of operating segments \| segment				4
Segment Reporting Information [Line Items]
Loss due to commodities market default allocated to junior capital	$ 8
Liability Waterfall
Segment Reporting Information [Line Items]
Loss due to commodities market default allocated to junior capital	$ 8	$ 8	$ 0	$ 8	$ 0