Federal Income Taxes (Federal Income Tax Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income tax expense (benefit), continuing operations [Abstract]
Current	$ 212	$ 220	$ 169
Deferred	64	263	218
Federal income tax expense (benefit)	276	483	387
Parent Company [Member]
Income tax expense (benefit), continuing operations [Abstract]
Federal income tax expense (benefit)	$ (66)	$ (77)	$ (73)