Summary of Significant Accounting Policies (details) - Updated Guidance - Subsequent Event [Member] - Scenario, Forecast [Member] - Accounting Standards Update 2016-01 [Member] $ in Millions	Jan. 01, 2018 USD ($)
Accumulated other comprehensive income, net of tax [Member]
New Accounting Pronouncements
Cumulative effect adjustment increasing (decreasing) equity	$ 22
Retained earnings [Member]
New Accounting Pronouncements
Cumulative effect adjustment increasing (decreasing) equity	$ (22)

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