Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

No definition available.

Name:	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Business and Basis of Presentation (Details) $ in Millions	Jun. 30, 2018 Company	Jan. 01, 2018 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of holding companies having outstanding public debt \| Company	2
Retained Earnings [Member] \| Accounting Standards Update 2016-01 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New accounting pronouncement or change in accounting principle, effect of change on net income \| $		$ 32