Federal Income Taxes (Federal Income Tax Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income tax expense (benefit), continuing operations [Abstract]
Current	$ 210	$ 88	$ 212
Deferred	(1,159)	178	64
Federal income tax expense (benefit)	$ (949)	$ 266	$ 276