Federal Income Taxes (Federal Income Tax Asset Liability) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Federal income tax asset (liability) [Abstract]
Current	$ (35)	$ 4
Deferred	(2,095)	(2,463)
Total federal income tax asset (liability)	$ (2,130)	$ (2,459)

Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, without jurisdictional netting.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319

Name:	us-gaap_DeferredTaxAssetsLiabilitiesNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant