Federal Income Taxes (Federal Income Tax Asset Liability) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Federal income tax asset (liability) [Abstract]
Current	$ (136)	$ (134)
Deferred	(1,867)	(3,024)
Total federal income tax asset (liability)	$ (2,003)	$ (3,158)

Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards, net of deferred tax liability attributable to taxable temporary differences.

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=6907707&loc=d3e32537-109319

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