Income Taxes Components of Income Tax Provision (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Components of income tax provision [Line Items]
Current Federal Tax Expense (Benefit)	$ 129	$ 667	$ 707
Current State and Local Tax Expense (Benefit)	59	27	36
Current Income Tax Expense (Benefit)	188	694	743
Deferred Federal Income Tax Expense (Benefit)	275	59	27
Deferred State and Local Income Tax Expense (Benefit)	69	52	(6)
Deferred Income Tax Expense (Benefit)	344	111	21
Income Tax Expense (Benefit)	$ 532	$ 805	$ 764